Always ensure your antivirus is active when browsing ROM sites. Legally, ROMs occupy a grey area; generally, it is recommended that you only download digital backups for games you physically own.
Below is a blog-style guide on how to safely navigate the world of retro game preservation. link download complete nes rom set
You have likely heard the rumor: "It is legal to download a ROM if you own the original cartridge and delete it after 24 hours." This is completely false. There is no such law or precedent anywhere in the world. It is a fabrication from early internet forums to justify piracy. Always ensure your antivirus is active when browsing
If you find a reputable link, the quality is usually excellent. The standard nowadays is the "No-Intro" labeling convention. ROMs occupy a grey area