More than enough. Especially since Rosetta’s orbital speed is no faster than a man walks. Plenty of time even for weak gravity to do its thing.
Thanks LW, as you said, more than enough. Distance is more significant than mass, such that a fairly puny and not very dense object like Pluto, which travels in an orbit well isolated from other bodies, can host a moon that is a giant fraction of its own mass (1/12th) at a distance about 1/12th that of the Earth-Moon distance. And Pluto has some other moons as well.