Canyonchasers.net recently went 'commercial' apparently, but they still have a decent guide for some local roads to check out, mostly in the western states.
http://www.canyonchasers.net/maps/We have some fun roads in northern Utah, if you are looking for somewhat technical roads, but it sounds like you are more focused down south. That being said, I still very much enjoyed Nebo Loop (near Provo), Monte is also gorgeous, and the Energy Loop is also a fun ride. Those are more geared to locals looking for a half day/full day outing, but you may be able to incorporate one or more of them into your own ride.
UT-14 also has some spectacular views, but I haven't done that on the bike yet (just in a car).
Do keep in mind that a lot of the higher elevation/less used roads in Utah may still be closed in May, depending on how fast the spring melt happens, so check UDOT's site if you are planning on any of these. Also, at least one road in southern Utah was taken out for the duration of the summer last year due to a rockslide, but I think that one has finally been fixed. Again, when in doubt check UDOT's site.
As for views, if you like National parks you have lots of options in Southern Utah.