You can just download the updated ROM sets, then use ClrMamePro to build the updated collection. The process involves a bit more than just copying over the updated ROMs, but it needs to do this because of the complexities of MAME. On Pleasuredome, there are links to just the updated ROMs. The last one, from 0.243 to 0.244 was only 8 MB.
You need to start off with a vanilla set, then apply each update as it comes out, ie., you can't directly update from 0.230 to 0.244. You have to find the updates from 0.230 > 0.231, 0.231 > 0.232 ... etc. I think Pleasuredome only links the latest update. If you're several versions out, it's just best to download the latest entire ROM set
Here is a link on a walkthrough to use ClrMamePro to update the set.