ROMs do not weigh anything. They are data. (I guess technically you could calculate the weight of the electrons required to modify the magnetic field of the Hard Drive Disk)...
Don't you mean the biggest ROM/ISO in terms of filesize? It's probably a PSX ISO like maybe Arc the Lad Complete which comes as a seven CD set.
Or maybe he means the biggest Romulation user? I weigh in at 260lbs. But I'm sure I'm not the biggest.
LOL, this is getting off topic. Anyway man you're heavier than me, I'm 210lbs but only 5'9" & that's a bit heavy for an average Filipino.
Go to the downloads section Set the filter to "File Size" "Descending" Sort. PSX 641MB https://www.romulation.org/PSX/Wing_Commander_IV_-_The_Price_of_Freedom_Disc_3_of_4_%5BU%5D_%5BSLUS-00272%5D.rar.html/ Sega Saturn 500.8MB https://www.romulation.org/Sega_Saturn/Soviet_Strike_(NTSC)_(U).exe.html/ Dreamcast 954MB https://www.romulation.org/Dreamcast/D2_Disc_3_of_4_(U)(HYKAN).rar.html/