Red Cone has some pretty steep sections, but it is definitely not as hard as holy cross. Rollovers are not uncommon on holy cross. The section you have to be careful on is the very steep and narrow descent at the end of red cone that comes down onto webster pass. If you come from the dillon side and go up webster pass and down handcart gulch (both moderately easy trails with narrow winding sections) you will be able to see this obstacle before you take it on. If it looks too dangerous for your liking, you can always turn around at the top of red cone.
If you do decide to descend the last part of red cone, make sure you select low gear, and just ride the breaks enough to keep you at a comfortable speed. If you lock up the brakes you will start sliding and could get sideways.
Wheeler's Lake trail is harder than red cone, easier than holy cross, and a lot of fun. Some technical obstacles that are easy with a good spotter and careful driver.