As a Utah native, I have been on all those roads, and biked on about half of them. The North Rim of the Grand Canyon is gorgeous and you shouldn't have a problem. Riding over Boulder Mountain will definitely be the toughest climb. Riding to Bullfrog marina will be great, albeit washboard dirt roads. I gotta say it though - you should keep going over to Canyonlands. If you like dirt and solitude, you could ride from Hanksville all on dirt roads to the Maze in Canyonlands which overlooks the Confluence of the Green and Colorado (which i think might be one of the least visited areas of any national park). You could ride the White Rim trail, or just cruz through Moab to Arches. The roads are probably a little more crowded in that area but really awesome. If you like hiking then check out the Henry Mountains which were the last mountain range mapped in the United States. Or you could spend a couple cool nights on top of Boulder mountain where there is a lot of good camping. The possibilities in the area are literally limitless and you could spend years down there never hiking the same gully twice.

Suggested reading:
Desert Solitaire by Ed Abbey
A Vagabound for Beauty by Everett Ruess

Have fun and hope to see you out there!