Prima di infornare le patate, le condisco con olio e rosmarino.

Prima di means before when it is followed by an infinitive.

So:

• Prima di infornare le patate = Before putting the potatoes in the oven

This is a very common Italian structure:

• Prima di uscire = before going out
• Prima di mangiare = before eating
• Prima di partire = before leaving

A useful contrast:

• prima di + infinitive = before doing something
• prima che + subjunctive = before someone does something

For example:

• Prima di infornare le patate... = before putting the potatoes in the oven
• Prima che le patate cuociano... = before the potatoes cook

In your sentence, the subject stays the same, so prima di + infinitive is the natural choice.

Infornare literally means to put into the oven.

So infornare le patate is not exactly the same as cuocere le patate:

• infornare = to put in the oven
• cuocere = to cook

That means:

• Prima di infornare le patate = before putting the potatoes into the oven
• not simply before cooking the potatoes

This verb is very common in cooking contexts. Its opposite is often sfornare:

• infornare = put into the oven
• sfornare = take out of the oven / remove once baked

In Italian, definite articles are used more often than in English, especially with general or familiar concrete nouns.

So Italian often says:

• le patate
• la pasta
• il pane

where English may simply say:

• potatoes
• pasta
• bread

In this sentence, le patate refers to the potatoes being prepared, so the article is perfectly normal.

Also, patate is feminine plural, so the article is le.

That le is a direct object pronoun, meaning them.

It refers back to le patate.

So:

• le patate = the potatoes
• le condisco = I season them

This avoids repeating the noun:

• Prima di infornare le patate, condisco le patate...
  This is grammatical, but repetitive.
• Prima di infornare le patate, le condisco...
  This is more natural.

Because patate is feminine plural, the matching direct object pronoun is also le.

Here is the pattern:

• lo = him / it (masculine singular)
• la = her / it (feminine singular)
• li = them (masculine plural)
• le = them (feminine plural)

In Italian, object pronouns usually go before a conjugated verb.

So:

• Le condisco = I season them
• literally: Them I season

This is normal Italian word order with pronouns.

Compare:

• Mangio le patate = I eat the potatoes

• Le mangio = I eat them

• Condisco le patate = I season the potatoes
• Le condisco = I season them

But with an infinitive, the pronoun is often attached to the end:

• devo condirle = I have to season them

So learners often notice this contrast:

• le condisco with a finite verb
• condirle with an infinitive

The verb is condire, meaning to season or to dress food.

It belongs to the -ire group, and in the present tense it uses the -isc- pattern in some forms:

• io condisco
• tu condisci
• lui/lei condisce
• noi condiamo
• voi condite
• loro condiscono

So condisco means I season.

This -isc- pattern appears in many common -ire verbs, such as:

• capire → capisco
• finire → finisco
• preferire → preferisco

Here condire means to season the potatoes, or more literally to add dressing/seasoning to them.

In cooking Italian, condire is very common for adding things like:

• oil
• salt
• pepper
• herbs
• sauce

Examples:

• condire l’insalata = to dress the salad
• condire la pasta = to add sauce/seasoning to the pasta
• condire le patate con olio e rosmarino = to season the potatoes with oil and rosemary

So in this sentence, season is probably the best natural English equivalent.

In Italian, when listing ingredients or substances after con, it is very common to omit the article.

So:

• con olio e rosmarino = with oil and rosemary

This sounds natural and idiomatic.

You could sometimes hear forms with articles in other contexts, but here the article-less version is the most normal for ingredients.

Compare:

• pasta con pomodoro e basilico
• carne con sale e pepe
• patate con olio e rosmarino

This is similar to English, where we also usually say with oil and rosemary, not with the oil and the rosemary.

Italian often drops subject pronouns because the verb ending already shows who the subject is.

Here:

• condisco already means I season

So io is not necessary.

Italian usually includes io only for emphasis, contrast, or clarity:

• Io le condisco, tu le friggi.
  I season them, you fry them.

In a normal sentence, le condisco is enough.

It can do both.

Le condisco is present tense, and in Italian the present can be used for:

1. a habitual action

   • Prima di infornare le patate, le condisco con olio e rosmarino.
   • This can mean: Before baking potatoes, I season them with oil and rosemary.

2. a recipe/procedural step

   • Italian often uses the present to describe what one does in a recipe or demonstration.
   • It can sound like: Before putting the potatoes in the oven, I season them with oil and rosemary.

So the tense is very natural here.

Yes, somewhat. Italian word order is flexible, though some versions sound more natural than others.

The original sentence is very natural:

• Prima di infornare le patate, le condisco con olio e rosmarino.

You could also say:

• Le condisco con olio e rosmarino prima di infornare le patate.

This is also correct, but it puts the main action first.

What you generally would not do is place the pronoun awkwardly after the verb:

• Condisco le con olio e rosmarino → incorrect

because the pronoun le must come before the conjugated verb:

• le condisco

Yes. That would also be correct.

• Prima di infornare le patate = before putting the potatoes in the oven
• Prima di mettere in forno le patate = before putting the potatoes in the oven

The version with infornare is simply more compact and especially common in cooking language.

So:

• infornare = a single verb, slightly more culinary/specific
• mettere in forno = more transparent and easy to understand literally

Both are good Italian.

It describes what is added to them when they are seasoned.

So:

• le condisco con olio e rosmarino = I season them with oil and rosemary

The preposition con here means with, introducing the ingredients used for seasoning.

It does not mean the potatoes are cooked by means of oil and rosemary; it means those are the seasonings added before baking.

This same structure is very common:

• condire con sale
• condire con pepe
• condire con olio
• condire con olio e limone

The comma separates the introductory time phrase from the main clause:

• Prima di infornare le patate, = introductory part
• le condisco con olio e rosmarino. = main clause

This is similar to English punctuation:

• Before putting the potatoes in the oven, I season them with oil and rosemary.

The comma helps readability and is very natural here, especially because the sentence begins with a subordinate phrase.