For robeto y yo shuold you use nosotros or ellos in your verb conjugation?

Here's why:

* Roberto y yo means "Roberto and I". This is a plural subject, indicating two people.

* Nosotros is the first-person plural pronoun, used for "we".

* Ellos is the third-person plural pronoun, used for "they".

Example:

Roberto y yo vamos al cine. (Roberto and I are going to the movies.)