He was saying to check the head code number on the side of the
cylinder head to know what engine it has in it!
But if you are sure that you have a RR SR20DE in it, here is the FSM for that engine. But it is from a 2000-2001 sentra so some of the electrical will be different and won't match what you have in your car, but the engine information will be the same.
I don't think I've ever seen anyone put a Roller Rocker in an SE-R. That's a first for me!
Here is the Factory service manual for a 2001 Sentra, which has the RR SR20DE engine in it. This may help a bit.
Index of /FSM/Sentra/2001_Sentra
And a 2000 Sentra:
Index of /FSM/Sentra/2000_Sentra