The weather is what it is and can change in an instant, especially in Colorado this time of year. This is has not been a big snow year for most parts of Colorado especially along the I70 corridor. As of right now, 70 is clear from Denver to GJ. But they're also forecasting snow for the weekend. If it does snow, its likely to disappear as fast as it came.
As far as traffic, your biggest concern will be ski traffic between Denver and Eisenhower tunnel. This will be heavy going west on Friday afternoon/evening and east on Sunday afternoon. Seems like you should be missing that.
Mapquest shows RC to GJ at about 650 miles and 10 hours. I find it to be faily reliable. It should take you 4 hours +- once you leave Denver to get to Grand Junction. Bear in mind getting through Denver could take awhile. Make sure you follow 76 to get from 25 to 70.
Grand Junction to Vegas is typically a very easy drive unless there's snow between Green River and Richfield. There's a small pass there, I forget the name. We typically do GJ to DL in one day, albeit a long one. Its right at 12 hours total travel time, door to door.
Be sure to check out goI70.com. Its a new website from CDOT that has real time traffic and weather. Have a great trip and let me know if you need any help finding your way around GJ!