El pollo con romero huele muy bien cuando sale del horno.

Because bien is an adverb, and here it modifies the verb huele (smells).

In Spanish, with verbs like oler, saber and sometimes verse, Spanish often uses bien/mal where English uses an adjective:

• Huele bien = It smells good
• Sabe bien = It tastes good
• Se ve bien = It looks good

Using bueno here would sound non-standard in Spain. For this sentence, huele muy bien is the natural choice.

Because oler can be used in two common ways:

1. To smell good/bad/strong/etc.

   • Huele muy bien
   • Huele mal
   • Huele fuerte

2. To smell like something

   • Huele a romero
   • Huele a pan
   • Huele a quemado

So in your sentence, huele muy bien means it smells very good, not it smells like... If you wanted to mention the specific scent, you could say:

• El pollo con romero huele a romero

It comes from the verb oler (to smell), which is irregular in some forms.

In the present tense, oler changes from o to ue in the same pattern as verbs like poder:

• yo huelo
• tú hueles
• él/ella huele
• nosotros olemos
• vosotros oléis
• ellos huelen

Two things to notice:

• The o → ue stem change happens in most forms.
• An h appears in forms like huelo, hueles, huele.

So huele means he/she/it smells.

Because Spanish often uses the present tense for general truths, habits, or things that normally happen.

This sentence sounds like a general statement:

• The rosemary chicken smells really good when it comes out of the oven.

So cuando sale del horno means when it comes out of the oven in a general, repeated sense.

If you were talking about a future event, Spanish would normally use the subjunctive after cuando:

• El pollo con romero olerá muy bien cuando salga del horno.
• The rosemary chicken will smell great when it comes out of the oven.

So:

• cuando sale = when it comes out / whenever it comes out
• cuando salga = when it comes out in the future

Because de + el contracts to del in Spanish.

So:

• de + el horno → del horno

This is a standard contraction, just like:

• a + el → al

Examples:

• Sale del horno = It comes out of the oven
• Voy al mercado = I go to the market

The only major exception is when El is part of a proper name:

• de El Escorial (not del Escorial if the official name is El Escorial)

Spanish uses definite articles more often than English does.

Here, el pollo can mean:

• the chicken as a specific dish being discussed
• or more generally chicken in the sense of the prepared item in this context

English might sometimes omit the article, but Spanish usually keeps it:

• El pollo con romero huele muy bien
• literally: The chicken with rosemary smells very good

This sounds natural in Spanish.

Con romero means with rosemary. It tells you one of the ingredients or seasonings.

• pollo con romero = chicken with rosemary

You may also hear pollo al romero, which usually means something more like rosemary chicken or chicken prepared in a rosemary style/flavouring.

So both are possible, but they are slightly different in feel:

• con romero = explicitly with rosemary
• al romero = a more set recipe-style expression

In this sentence, con romero is perfectly clear and natural.

Here it means chicken as food, not the live animal.

Spanish, like English, often uses the same word for the animal and the meat:

• un pollo = a chicken
• comer pollo = to eat chicken

Because the sentence mentions romero and el horno, the context clearly shows it is talking about the dish.

Because the subject is el pollo, which is singular.

The main verb of the clause cuando sale del horno agrees with el pollo:

• el pollo ... sale
• los pollos ... salen

Even if in English you might think of chicken as pieces, Spanish is treating it here as one dish or one whole item, so singular is correct.

The given order is natural, but Spanish allows some flexibility.

Original:

• El pollo con romero huele muy bien cuando sale del horno.

You could also say:

• Cuando sale del horno, el pollo con romero huele muy bien.

That version puts more emphasis on the time clause when it comes out of the oven.

Both are correct. The original word order is probably the most neutral and natural if you are simply making a statement.

In Spain, huele is pronounced roughly like WEH-leh.

A few useful pronunciation points:

• h is silent in Spanish
• ue here sounds like we
• the stress falls on the first syllable: HUE-le

So although it is spelled with h, you do not pronounce the h at all.