Are you looking to acquire ROMs to make a personal archive yourself or submit ROMs to Vimm's Lair so that they can be archived?
If it's the former there are better sites out there for downloading complete sets. You can check the megathread (check the sidebar) but using Internet Archive in combination with a reputable download manager is usually what people do. Myrient is relatively new and seems good as well.
Vimm's Lair is better suited for downloading individual very specific titles.
ex. the North Korean version 1.02 of Shrek 5: The Swampening for the Super Playstation
If it's the latter each console's page has a section that lists what games are missing and their hash values. If yours match you can simply compress and send it.