Watching practice two this morning, and I note that the Rolex sponsorship is present during break bumpers on Sky Sports F1. Santander, their previous title sponsor, pulled out at the end of last season.
Given Rolex’s increased presence in Formula 1 this year, the move makes logical sense. I will hunt around for something official later.
Update at 06:09: Shell are also a sponsor for 2013 it appears, so they have multiple sponsors. That is reminiscent of the Eurosport days in the mid 90s where they had multiple sponsors.