The Kingfisher Fly Shop has your Rock Creek Fishing Report right here:
The streamer fishing is day to day and section to section on the creek these days, but if you hit it right, there are some good fish to be had. Dry fly fishing has been very solid during the heat of the day. Believe it or not, ants have been working especially well, but mahogany type stuff is the gold standard. The best window for top water action has been getting smaller and smaller and is best now from about 2 to 4. You can hook up pretty consistently subsurface on a variety of nymphs including copper Johns, San Juans, rubber legs, and other standard fare.
HATCHES: hoppers, BWOs, PMDS, Caddis, October Caddis, Mahoganies, Hecubas