Tata kupuje rogaliki i parówki na sobotnie śniadanie.

Tata means dad and is the normal, warm, everyday word used in speech and in simple sentences.

Ojciec also means father, but it sounds more formal, more neutral, or sometimes more official.

So:

• tata = dad
• ojciec = father

In a sentence like this, tata sounds very natural.

At the beginning of the sentence, Polish capitalizes the first word, just like English does.

So Tata is capitalized here simply because it starts the sentence, not because it is a proper name.

If it appeared in the middle of a sentence, it would normally be tata, for example:

• Mój tata kupuje rogaliki.

Kupuje is the present tense of the imperfective verb kupować.

It is used for:

• actions happening now
• habitual/repeated actions
• general statements

So Tata kupuje... can mean:

• Dad is buying...
• Dad buys...

By contrast, kupi is from the perfective verb kupić and usually refers to a completed future action:

• Tata kupi rogaliki = Dad will buy croissants/rolls

So in your sentence, kupuje presents the action as ongoing or simply describes what he is doing.

They are in the accusative plural, because they are the direct objects of the verb kupuje.

Dad is buying what?

• rogaliki
• parówki

That makes them direct objects, so Polish uses the accusative.

In this sentence, the accusative plural looks the same as the nominative plural:

• rogaliki
• parówki

So the form does not change, but the grammatical role does.

Because for these nouns, the accusative plural happens to be the same as the nominative plural.

That is very common in Polish.

For example:

• singular: rogalik
• plural nominative: rogaliki
• plural accusative: rogaliki

And:

• singular: parówka
• plural nominative: parówki
• plural accusative: parówki

So even though they are objects, their forms stay the same.

Here na means something like for in the sense of for a purpose / intended for.

So:

• na śniadanie = for breakfast
• na obiad = for lunch
• na kolację = for dinner/supper

In this sentence, na sobotnie śniadanie means for Saturday breakfast or for breakfast on Saturday.

This is a very common Polish pattern:

• kupić coś na śniadanie
• zrobić coś na obiad
• przygotować coś na kolację

Because sobotnie has to agree with śniadanie.

The noun śniadanie is:

• neuter
• singular
• here in the accusative

For neuter singular, the adjective form is -e, so:

• sobotnie śniadanie

Agreement in Polish means the adjective must match the noun in:

• gender
• number
• case

That is why you do not get sobotni śniadanie.

It is in the accusative singular.

With na, Polish can take different cases depending on meaning, but here na expresses purpose/intended use, so it takes the accusative:

• na śniadanie
• na obiad
• na kolację

In this specific noun, śniadanie, the nominative and accusative singular look the same, so you do not see a visible change in the ending.

Polish does not have articles like a/an and the.

So Tata kupuje rogaliki i parówki does not explicitly say:

• Dad is buying croissants and sausages
• Dad is buying some croissants and sausages
• Dad is buying the croissants and sausages

The exact English article depends on context.

Polish usually leaves that information unstated unless something else makes it clear.

No, Polish word order is relatively flexible.

Tata kupuje rogaliki i parówki na sobotnie śniadanie is a very normal, neutral order.

But other orders are possible, for example:

• Na sobotnie śniadanie tata kupuje rogaliki i parówki.
• Rogaliki i parówki tata kupuje na sobotnie śniadanie.

These versions can shift emphasis or sound more marked, but the basic meaning stays the same because Polish uses case endings, not just word order, to show grammatical roles.

Yes, rogaliki is the plural of rogalik, which is related to róg / rogal and often has a diminutive feel.

In practice, though, rogalik is also just the normal name of a small crescent-shaped pastry or bread roll. So even if it historically has a diminutive form, learners should often treat it as a standard food word.

So:

• rogalik = one roll/crescent pastry
• rogaliki = several

Yes. In natural English, both can work depending on context.

Literally, the phrase is something like for Saturday breakfast, but in normal translation you might say:

• for Saturday breakfast
• for breakfast on Saturday

The Polish phrase naturally covers the idea that the food is intended for that meal.

Yes.

Because kupuje is imperfective present, it can describe:

• something happening now: Dad is buying...
• a usual action: Dad buys...

So without more context, the sentence could mean either:

• Dad is buying croissants and sausages for Saturday breakfast or
• Dad buys croissants and sausages for Saturday breakfast

Context tells you which reading is intended.

Polish often leaves that idea unspoken.

English frequently says:

• some croissants
• some sausages

But Polish can simply say:

• rogaliki
• parówki

If the speaker wants to emphasize quantity, they can add something, for example:

• jakieś rogaliki = some croissants/some kind of croissants
• kilka parówek = a few sausages

But in your sentence, no extra word is needed.