I don't want to turn you off the Rokinon's because I've never used one and in general they seem to be very good, and fast. I've stuck to AI-s because they are the most recent of the fully manual. superbly constructed series. AI are mostly fine too - but I wouldn't buy an earlier lens personally, mainly because of coatings.
After much research, this is the set I'm slowly building:
24mm 2.8 AI-s
28mm 2.8 AI-s
35mm f2 AF-D
50mm f1.8 AI-s (1st version: serial no's 3135197 - 3304551)
85mm f2 AI-s
105mm f2.5 AI-s
135mm f2.8 AI-s or E-series
200mm f4 AI-s
I believe that these lenses represent the best balance of sharpness, speed, size and cost of all Nikon's manual lenses. They also all have a 52mm filter thread, which is very handy in terms of carrying a ND filter around. I already have the 24, 35, 50 and 85, and they are all excellent. The 35mm is my 'normal' lens and has probably been on my camera the most. I just use the 18-55 kit for very wide stuff at the moment (I have my eye on the Sigma 18-35 1.8 but it's very big).
If I could only take three lenses in my bag and they had to be from the list above, I would probably go with the 28, 50 and 105 (these all have absolutely stellar reputations and cover a decent, if slightly long range). If I wanted to cover a wider range, the 24, 35 and 85 would probably be my choice. If you want to supplement the list with a zoom or AF prime you already own, I think you could probably choose any of them to fill the gaps you need and be happy.
It might be worth asking Brando Li his opinion on this, as he has used both Rokinon and AI-s glass quite a bit I believe (though I'm not sure which Nikkors).