If you are flipping a house, or renting it out, you can calculate an ROI. Otherwise, if you plan to live in it indefinitely, there is no ROI to calculate - lots of money going in, no money coming out. Yes, you might sell the house someday and make some money but that day is probably far off and the price it will sell for is impossible to predict. Boulder might keep going nuts (we just sold a really crappy place there for $270k that had appreciated too much to keep as a rental, things are crazy there) or it might not.
Historically house prices rise at about 1% over inflation so non-flip/non-rental primary residences aren't fantastic investments in general. Obviously you can do much better if you get lucky, or you can do much worse.
-W