The route is straightforward: follow the closed section of Gold Camp Road up to the collapsed tunnel, then follow the St. Marys Falls trail up to and past the falls, then head west to climb switchbacks up the east side of Rosa's north ridge. Once on the ridge, the final section is more trail through gradually thinning trees, up the north side to the summit. Actually, I lost the trail in this last section, as it was covered in up to three feet of snow, and had to do some rather slow bushwhacking and postholing. The ridge is easy to follow, however, and the summit did not disappoint, with marvelous clear-skies views of the Sangre de Cristo range off to the south, the southern Sawatch to the southwest, and Pikes Peak to the northwest.
With better conditions (i.e., summer!) I've made the round trip in the same time it took me to do the ascent this time. It was still a rewarding adventure, especially since I didn't see a single other person on the trail! The most recent entry on the summit register was from the 27th of last month. (Apologies for no pictures: I only took a few, and I still haven't figured out how to include them in these TRs :( )