Why not??? Ms. Brown has been examined for years, there can't be any more surprises here in discovery. The Senate allready confirmed her this year so it would be hard for the Rats to say she wasn't qualified. This would get the Court the woman/minority position (even if she isn't black enough for some or woman enough for the left). Confirmation of Roberts would send Reinquist the signal he needs to retire, so Bush might as well hit another homerun with Brown.
she's qualified, but 2 straight from the DC Circuit, if you count Ginsburg, that's 3 of the last 4. it just seems likely that they'd look elsewhere.
perhaps Bush chose Roberts to Pplease the Chief and is holding Brown for the first female/black Chief? it seems like a good stategy