Beane always said when he was going to draft a QB that wasn't system dependent yet Roman seems to thrive with QBs that are less arm talented. If we do lose Dorsey I'd think that next man up be either Joe Brady, Chad Hall or Mike Shula for our OC.
I'd imagine the Ravens will franchise tag Lamar and keep him for 1 season with a new OC, if he excels with the new OC then he gets a long term deal otherwise he's gone and they find a new QB that meets the new OC style of offense better.