Hi Nathan,
Yes, it's still legal to buy, sell, and keep roundtails (although they are likely to be banned from commercial collection soon). Since the roundtail is not a California species, there are no laws there about keeping them.
As far as the care sheet goes, I don't know of one specific to roundtails. However, their general care is going to be very similar to that of other HLs. I would think a good care sheet for desert HLs would provide adequate instructions for roundtails as well. The only difference would probably be the fact that being smaller lizards, the roundtails will take smaller prey, though they do eat harvester ants. You might also look in the old forum archive where there were quite a few posts about the care of roundtails.
Could you post the link to the roundtails (or e-mail it to me: gvilla@fau.edu ? I like to keep track of sites that sell HLs.
Thanks
Gary