Hoy había una oferta de papel higiénico, así que compré dos rollos.

Había is the imperfect of haber used impersonally, meaning there was / there were. Here it sets the scene: today, there was a special offer.

• Había sounds natural for background information or a situation that existed.
• Hubo would sound more like a specific event that occurred, which is less natural here.
• Estaba would mean it was, not there was, so it would not work for introducing the existence of an offer.

So Hoy había una oferta... is a very natural way to say that earlier today there was a deal available.

Starting with Hoy puts the time first and gives context immediately: Today, there was a special offer...

This is very common in Spanish. Time expressions are often placed at the beginning of the sentence to frame what follows.

You could also say Había una oferta de papel higiénico hoy, but that is less natural in this context and sounds more like an afterthought.

Here una oferta means a special offer, a deal, or a promotion in a shop.

In Spain, oferta is very commonly used for discounted supermarket items or limited-time deals.

It does not necessarily mean a formal offer in the English business sense. In everyday shopping Spanish, it usually means some kind of bargain.

In Spanish, oferta de + noun is a very common way to mean an offer on something.

So:

• una oferta de papel higiénico = a special offer on toilet paper

Using en would not be the normal choice here. Spanish often uses de where English uses on in this kind of shopping expression.

After de, Spanish often leaves out the article when talking about a product in a general sense.

So:

• una oferta de papel higiénico = a special offer on toilet paper

This sounds more natural than una oferta del papel higiénico, which would suggest a more specific, already identified toilet paper.

In other words, papel higiénico here means the product category, not a particular pack.

Así que means so, therefore, or so as a result.

It links the cause and the result:

• there was a special offer
• so I bought two rolls

It is very common in everyday Spanish and sounds natural in both speech and writing.

Compré is the preterite, used for a completed action: I bought.

That fits because buying the two rolls is a single finished action.

Compraba would be imperfect and would suggest something ongoing, repeated, or descriptive, such as:

• Cuando veía ofertas, compraba papel higiénico. = When I saw deals, I used to buy toilet paper.

In this sentence, the speaker is talking about one completed purchase, so compré is the right tense.

Spanish often includes the unit or container more explicitly than English.

Here dos rollos means two rolls. That is the normal full expression.

In conversation, if the context is very clear, someone might shorten it and say just compré dos, but dos rollos is clearer and more complete.

Here rollo means roll, as in a roll of toilet paper.

But rollo has several meanings in Spanish depending on context. For example, in casual speech it can also mean things like:

• a boring thing or a drag
• a vibe or dynamic
• a fling or casual relationship

In this sentence, though, the meaning is simply the literal physical roll.

Yes, Hoy había... is completely natural in Spanish.

Spanish often uses the imperfect like this to describe a situation that existed at some point during the day. It can feel a bit like:

• Earlier today, there was...
• Today, there happened to be...

So even if the literal English structure feels slightly unusual, the Spanish is perfectly idiomatic.

They are related, but not exactly the same:

• oferta = a special offer or deal
• descuento = a discount, the actual reduction in price
• rebajas = sales, especially seasonal sales

In this sentence, oferta is the best choice because it refers to a shop promotion on a product.

The accent marks show which syllable is stressed and sometimes distinguish forms clearly.

• había: the accent helps show the stress and that -ía is pronounced clearly
• así: the stress falls on the last syllable
• compré: the accent marks the first-person preterite form I bought

These accents are important in writing and are not optional.

Yes, but the nuance changes slightly.

In Spain, he comprado is very common for a recent action connected to the present, especially with time expressions like hoy:

• Hoy ha habido una oferta..., así que he comprado dos rollos.

That version is also very natural in Spain.

The original sentence uses había + compré, which sounds like the speaker is narrating what happened earlier today as a completed little story. So both are possible, but the original has a more narrative feel.