installed roller rocker arms today but i feel something is wrong..
do they need special studs or studs are all same?
7/16 was standart on my previous heads i am using them.
is there anything like non-roller and roller?

Roller rockers USUALLY come with locking adjuster that use a set screw to JAM the adjuster into place (Poly-Locks, they are called). Do NOT use the cheap-o crushed locknuts that are used on a factory adjustable rocker setup.

7/16 screw-in studs are standard on MkIV big block heads, and most aftermarket heads. Bolt-down rockers are used in Gen5 and Gen6 heads, and use a 3/8" bolt or stud. Conversion studs are available that have a 7/16 nub sticking above the hex on the stud with 3/8 below screwed into the head. For HP applications, it is "better" to drill and tap the heads to use full 7/16 old style studs.

There are also ARP heavy duty studs available.

Bottom line is that if your heads had good old 7/16 studs in them, you're fine. You can upgrade to ARPs if you wish, but just making sure you use good poly locks is the only thing important.

I don't think any BigBlock heads used "press in" studs like some smallblock heads (somebody correct me if I'm wrong). Those are not suited at ALL for a performance application.

If the studs are old and used, change them. I was surprised when I started breaking studs for no apparent reason. Changed them all to ARP's and have never had that happen again. If you are using roller rockers with polylocks, the top of the stud should be flat so the set screw bites into a flat surface.

The center shaft for the roller rockers is " D " shaped. Make sure the flat side of the " D " is facing up, not the rounded side.
When you snug down the poly locks, go a half turn past zero lash, tighten the lock on top and then give the nut another 1/8 or so turn to make sure they stay on tight.

If you're running into a clearance issue between the roller rocker and the spring retainer (and this is something you better be looking for) you'll need to check the valve train geometry. You can buy longer studs if you need them, but if there's a clearance issue at the retainers you'll be needing longer pushrods first.