Final answer:
The correct Spanish conjugation of the verb 'to have a birthday' is 'cumple años'.
Step-by-step explanation:
The correct Spanish conjugation of the verb 'to have a birthday' is 'cumple años'. In the given sentence, the correct form to use is 'cumple' because the subject is 'Mi amiga Rosa' which is the third person singular form. The conjugation 'cumplir' means 'to have' and 'años' means 'years'.
Learn more about Spanish verb conjugation