El romero cambia la textura de la salsa, y el tomillo también le da buen aroma.

In Spanish, it is very common to use the definite article with ingredients, plants, and foods when talking about them in a general way. So el romero and el tomillo sound natural in Spanish, even though in English we often just say rosemary and thyme without the.

This happens a lot with foods and substances:

• El ajo da mucho sabor.
• La cebolla está muy cara.
• El aceite es importante en esta receta.

So the article here is not necessarily pointing to one specific piece of rosemary or thyme; it is just the normal Spanish way of referring to those ingredients.

The verb cambiar can be used directly with a thing that changes, without needing a.

So:

• cambiar la textura = to change the texture
• cambiar el color = to change the color

You use a with cambiar in other structures, especially when something changes into something else:

• Cambió el azúcar por miel = He/She replaced sugar with honey
• La situación cambió a peor = The situation changed for the worse

But in your sentence, la textura is the direct object of cambia, so no a is needed.

Le refers to la salsa.

So the structure is:

• el tomillo = subject
• le da = gives to it
• buen aroma = a good aroma
• le = to it, meaning to the sauce

A fuller version would be:

• El tomillo también da buen aroma a la salsa.

Spanish often uses an indirect object pronoun like le even when the noun is already understood or could be added later. This is very natural:

• Le da sabor = It gives it flavor
• Le añade color = It adds color to it

Yes, absolutely. That version is correct and very clear.

Compare:

• El tomillo también le da buen aroma.
• El tomillo también da buen aroma a la salsa.

Both are natural. The version with le sounds smoother when la salsa has already been mentioned, as it has in the first part of the sentence. Spanish often avoids repeating the noun if it is already obvious.

You can even hear both together:

• El tomillo también le da buen aroma a la salsa.

That is grammatically fine too, because Spanish often uses the pronoun and the noun phrase together for clarity.

Bueno becomes buen before a singular masculine noun.

Since aroma is masculine singular, you get:

• buen aroma

This is a very common shortening:

• un buen libro
• buen tiempo
• buen sabor

But after the noun, it stays bueno:

• El aroma es bueno.

So:

• buen aroma = correct
• aroma bueno = possible, but it means something slightly different in emphasis and sounds less natural here
• bueno aroma = incorrect before the noun

Some Spanish nouns ending in -a are masculine, especially words of Greek origin. Aroma is one of them, so it takes masculine articles and adjectives:

• el aroma
• un aroma intenso
• buen aroma

Other common masculine nouns ending in -a include:

• el problema
• el sistema
• el tema
• el clima

So even though aroma looks feminine to an English speaker, it is grammatically masculine.

También means also or too, and its position can shift slightly depending on what you want to emphasize.

In your sentence:

• El tomillo también le da buen aroma.

This most naturally means thyme also gives it a good aroma, in addition to what rosemary does.

Other placements are possible:

• También el tomillo le da buen aroma.
  This puts more focus on el tomillo itself, as in thyme too.
• El tomillo le da también buen aroma.
  This is possible, but less neutral here.

For learners, the most natural default is often to place también before the verb or just after the subject, as in your sentence.

The comma is used because the sentence joins two related clauses:

• El romero cambia la textura de la salsa
• y el tomillo también le da buen aroma

In Spanish, a comma before y is less common than in English, but it can still appear when:

• the two clauses are long,
• the writer wants a slight pause,
• or the clauses have different subjects, as here: el romero and el tomillo.

So the comma is acceptable and helps readability, but you may also see:

• El romero cambia la textura de la salsa y el tomillo también le da buen aroma.

That version is also correct.

In the first clause, de la salsa is stated explicitly:

• cambia la textura de la salsa

In the second clause, Spanish avoids repeating a la salsa because it is already understood:

• el tomillo también le da buen aroma

The pronoun le stands in for a la salsa.

This kind of economy is very common in Spanish. Once the thing being talked about is clear, Spanish often switches to a pronoun instead of repeating the noun.

No, not in this sentence.

Here is why:

• dar algo a alguien/algo = to give something to someone/something
• buen aroma is the thing being given
• la salsa is the receiver

So la salsa is an indirect object, and the pronoun for that is le, not la.

Compare:

• Le da buen aroma = It gives it a good aroma
• La cambia = It changes it

So:

• cambia la textura → direct object
• le da buen aroma → indirect object pronoun

Yes. It is a natural and common way to talk about ingredients affecting the smell of food.

Examples:

• El ajo da mucho aroma al guiso.
• Las hierbas dan aroma al pollo.
• El vino le da aroma a la salsa.

You may also hear related expressions such as:

• dar sabor = to give flavor
• dar olor = to give smell
• aportar aroma = to contribute aroma

In cooking contexts, dar aroma sounds very natural.

Yes. It sounds like a general statement about cooking and the effects of these herbs.

Spanish often uses the present tense this way:

• El romero cambia...
• el tomillo también le da...

This can describe:

• a general fact,
• a typical result,
• or what usually happens in a recipe.

So it does not have to mean one single specific occasion. It can mean something like rosemary changes the texture of sauce, and thyme also gives it a nice aroma as a general cooking observation.