You most certainly can...if the flashing itself is coming up, the repair is a little extensive in that you will have to remove the old flashing...but if it's just the roofing cement leaking a little you can get either caulk tubes of it gallon buckets...at any rate hopefully it just needs some new tar over it...and while your at it, check all the plumbing vent boots too....this should be check for tar cracks yearly anyway (like I remember to do it!)...hope it's an easy fix!
Allen