Now - with the next nominee whoever he/she is - they can vote as a block - claiming principles. They will be able to point to the dim votes for Roberts and say "See? We're not in lockstep but this nominee MUST not be confirmed."
... my two cents. ;-)
And they'll probably have at least a few RINOs (Chafee, Snowe, Collins at a minimum) joining them in opposing the next nominee.