ROMS do not change... roms are roms and just dumps of chips from cartridges or from arcade boards and any system that has chips. The problem in emulation is that most folks refer to anything you load into an emulator is a rom.... it isn't. Tapes, disk images, hard drive images, cd/dvd all are not roms even though the masses refer to them as such.
higan would be a better option for SNES and it also emulates other systems. I also agree with Keetah that space for emus is not an issue as it's a small part of the space needed for emulation especially for modern systems. ccs64 is a nice C64 emu and Vice is as well and covers many Commodore systems.
Since you say sources where you get stuff are/can be shady why don't you just download emulators from their homepage?