If you want to avoid the mountains, take I-80 across the Rockies instead of I-70. Not nearly so scenic, but not such high passes. If you want to take this route and really want to avoid Denver, take US 385 north of Burlington to Wray, east on US 34 to Greeley, north on US 85 to I-80.
But I-70 through Colorado is worth the drive just for the scenery. To get to Vernal, we take CO 13 north of Rifle to CO 64 through Rangely up to US 40 and on to Vernal. We go to Vernal every few years from Glenwood Springs and this is the quickest route we take for fewest hills and easiest towing. But you can't easily avoid going through Denver if you want to go on I-70, so just avoid rush hour and go for it.