The easiest and quickest fix would probably be to switch to using the 2D API instead. Using it, you could create the text on a bitmap, then rotate it before drawing it to the roScreen. I don't know how complex your screen layout is, but figuring that out would almost certainly be a lot faster than waiting on Roku to release a firmware update to fix text rotation on the roImageCanvas. Just my opinion...
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)