There's no good way to do it (yet) in romlister, but that's on my todo list.
However, *if* you have your ROMs folder filled with only the zip files that match your list, you can use romlister's rom scan utility to re-create it and output it in other formats:
1) create a merged xml file
2) hit the "rom scan" button and point romlister to your ROMs folder.
3) RL will then trim down that merged xml file to just the ROMs that it finds
4) Click the "list all roms" button and then throw all of those roms into a new list, output it in any format you want.
a PITA, yes.
the more you bug me about this feature, the more peer pressure I have to do it, so pile it on.

edit: should note that this is only going to work for MAME roms...