You can use SUPER to convert the rmvb/rm files to vob files I believe. SUPER lists rm/rmvb support. SUPER is free to download and use, but the actual download is hard to find at their site. It is at the bottom of the third page, and they don’t allow direct links to it.
In order to have the converted vob files play on a regular player, you will have to use an authoring program to get the necessary ifo and bup files that are found in dvd video. You should be able to import the vob files into DVDStyler which is a free authoring program, and make your dvd. The SUPER site recommends using TMPGenc Author, but it is not a free program.
Here is the DVDStyler home page: http://www.dvdstyler.de/
If you want an all in one solution, I’d suggest ConvertXtoDVD. It is commercial product, about $50 these days I believe.