Roca has moved to Bayern from Barca's local rivals Espanyol and was presented to the local media yesterday.
And he admits he enjoyed watching Bayern thrash Barca 8-2 in last season's Champions League clash in Lisbon.
Roca said, "We know that there is a great rivalry between Barcelona and Espanyol. Obviously, I supported Bayern and I was very happy afterwards, although it is clear that a result so big was surprising for everyone.
"The superiority they showed on the field was something impressive to see."
He also stated: "I am very happy to be here. It is a great opportunity to learn from the best and to grow as a footballer. I promise to give my best with confidence, effort and work."