Rollie is clearly 1A while Fernandez is 1B. Rollie will start out, if he faulters or doesn't feel great, Fernandez will step in.
I'm not sure how you came to that conclusion (the word clearly bothers me a little bit), but I think you are right about the game split. Fernandez has been the dominant goalie of the two in the preseason, but that's an annual routine- Manny is steaming hot early on, then cools down, gets injured a couple of times, and the more consistant Roloson ends up taking over. We've been through this before...
If you look at career stats, Fernandez has been consistently better than Roloson. For 3 of the last 4 seasons Fernandez has posted a winning record, a GAA around 2.2, and a save % around .920. The only abberation was 01-02, where he had injury issues that affected his performance. If you look at Rollie's career stats, last year was the abberation, clearly a career year. You could also argue that he's improved, as his stats show steady improvement in most areas. I still think his numbers will fall off some this season, whereas Manny's will stay pretty much the same.