Here's a simple tutorial on how to install a N64 (Nintendo 64) emulator on you iPhone 4, iPhone 4S, iPad 1, iPad 2, iPad 3. And how to get roms. I do not recommend this on any iDevice lower than iPhone 4 due to performance issues.
In this case we will be using an iPhone
Step 1: Have your jailbroken iPhone ready. If you haven't already, search how to jailbreak iPhone on Google or YouTube. You will need to have Cydia for this to work.
Step 2: Go into Cydia on your iPhone. Search for "N64iPhone Free". Download it and make sure it opens without any problems. If you do encounter a crash when opening it. Go into Cydia and hit reinstall and try it again.
Step 3: Set up an SSH program on your Computer (Mac or Windows) I recommend WinSCP for windows, you can Google search "SSH for mac" for mac computers. Once you have that downloaded, set it up by following the on screen instructions. Its easier than it sounds.
Step 5: keep that SSH program running, open up your browser and go onto Coolroms.com.
Go into the N64 category and download the roms of your choice. Save it to your desktop for easy access.
Step 6: Drag and drop the folder you downloaded into your SSH program. You can close that SSH program and go back to your iPhone. Open up the app. You should see the N64 game you downloaded in the list. Play the game and enjoy!
This works on these IOS firmwares: 5.0.1, 5.0, 4.3.5, 4.3.4, 4.3.3, 4.3.2, 4.3.1, 4.3, 4.2.10, 4.2.9, 4.2.8, 4.2.7, 4.2.6, 4.2.5, 4.2.1, 4.2, 4.1, 4.0.2, 4.0.1, 4.0, 3.2.2, 3.2.1, 3.2, 3.1.3, 3.1.2, 3.1, 3.0.1, 3.0