Wieczorem jem ciepłego naleśnika z serem, a rano wolę rogalik.

Polish often expresses time with a single adverb or a noun form used adverbially, without a preposition.

• wieczorem = in the evening
• rano = in the morning / early in the morning

So Polish does not need a word like in here.

A useful detail:

• wieczorem comes from wieczór and is an instrumental form used adverbially.
• rano is just an adverb.

This is very normal in Polish:

• latem = in summer
• zimą = in winter
• nocą = at night

Jem is the 1st person singular form of jeść: I eat.

In Polish, the same present-tense form can mean either:

• I eat in general / habitually
• I am eating right now

In this sentence, because of wieczorem and rano, it is understood as a habit or usual preference, not something happening at this exact moment.

This is one of the most interesting parts of the sentence.

By the basic textbook rule, naleśnik is a masculine inanimate noun, so in the accusative singular you might expect:

• jem ciepły naleśnik

But in real Polish, especially with names of foods, many speakers often use an animate-like accusative:

• jem ciepłego naleśnika
• zjem pączka
• kupię burgera

So ciepłego naleśnika is a very natural everyday form for many people.

The adjective matches the noun:

• ciepłego
  • naleśnika

If you see ciepły naleśnik in a textbook, that follows the simpler standard pattern. If you hear ciepłego naleśnika in speech, that is also very common.

Because the preposition z meaning with requires the instrumental case.

So:

• ser = cheese
• z serem = with cheese

This is a very common pattern:

• z cukrem = with sugar
• z mlekiem = with milk
• z dżemem = with jam

Be careful: z can also mean from / out of, and then it usually takes the genitive, not the instrumental. But here it clearly means with.

A often connects two clauses with a contrast or comparison.

In this sentence, it means something like:

• and
• while
• whereas

So the sense is:

• In the evening I eat ..., and/whereas in the morning I prefer ...

It is not as strong as ale (but in the stronger sense).
Here a is perfect because the speaker is simply contrasting two times of day.

Because wolę means I prefer, while lubię means I like.

So:

• lubię rogalik = I like a croissant/roll
• wolę rogalik = I prefer a croissant/roll

In this sentence, the speaker is not just saying they like both things. They are saying that in the morning their preferred choice is rogalik.

Here the speaker uses the regular accusative of a masculine inanimate noun, which is the same as the nominative:

• rogalik

That is the straightforward, neutral pattern.

You may sometimes hear food words with -a in the accusative in everyday Polish, but that does not happen equally with every noun or for every speaker. So:

• rogalik is perfectly normal here
• some speakers might also say rogalika in colloquial speech, but rogalik is the safer basic form to learn

So the sentence mixes:

• a very common food-style accusative: naleśnika
• a regular accusative: rogalik

That kind of variation is normal in real Polish.

Because Polish has no articles.

So Polish does not have direct equivalents of English:

• a
• an
• the

Whether something is understood as a warm pancake, the warm pancake, a roll, or the roll depends on context.

That is why the sentence can be perfectly natural without any article words.

No. Polish word order is relatively flexible.

This sentence starts with Wieczorem and rano to highlight the contrast between the two times of day:

• Wieczorem jem ...
• a rano wolę ...

That is a very natural choice.

You could rearrange parts of the sentence, but the emphasis would change. For example:

• Jem wieczorem ciepłego naleśnika z serem, a rano wolę rogalik.

This still works, but the original version sounds especially good because it puts the time expressions first and makes the contrast clear.

It can absolutely describe a general habit.

In Polish, using the singular in a sentence like this often means a typical choice:

• in the evening, I eat a warm pancake with cheese
• in the morning, I prefer a roll/croissant

It does not have to mean exactly one item every single time. It is simply the natural way to describe a usual preference or routine.