Learn Romanian: De Paște mâncăm ouă roșii și cozonac. - At Easter we eat red eggs and cozonac.

In Romanian, when talking about what happens on a holiday generally, you use de (like de Crăciun for 'at Christmas' or de Paște for 'at Easter'). This translates to 'on the occasion of'. You would use la for physical locations or specific gatherings, but major holidays take de.

I have also seen Paști instead of Paște. Which one is correct?

Both Paște and Paști are correct and widely used. Paște is a singular form, while Paști is plural. You will hear both de Paște and de Paști, though de Paște is generally more common in modern everyday speech.

Ou (egg) is a neuter noun. Why is the adjective roșii rather than ending in '-e'?

Because ou is neuter, its plural ouă takes the feminine plural form of adjectives. The adjective roșu (red) is a bit irregular; its feminine plural is roșii, not 'roșe'. So we get ouă roșii.

Why is there no article for cozonac here?

Just like in English ('we eat cake'), Romanian drops the article when referring to a general category of food or an unspecified quantity. If you said mâncăm un cozonac, it would mean 'we eat one whole loaf of cozonac'.