The RPI 2 & 3 cpu is too slow for N64 and also the gpu poor at rendering 3D graphics.
If you really wanna run N64 roms without being slow then look into the Odroid N2 which flys for N64 / Dreamcast / Naomi / Atomiswave / playstation 1 emulation and many others 🙂 .. i had a RPI3B+ but the Odroid N2 blows it out the water 🙂