Picked up a Rock Island .38 super that somebody had changed the trigger group and grip safety on. It fuctons well but randomly (every ten shots or so) when the trigger is pulled its as if I am pulling it without pushing in the grip safety. If I let the grip safety out and squeeze again it usuall corrects the problem, sometmes I have to depress and release it 2 or 3 times. Im no 1911 expert so I need some advice on how to correct this issue. Thanks.

sound's like the grip safety wasn't fit correctly.  Send it to RIA to get fixed.

Rock Island is not an icon of firearms quality, so there may an issue there.

However technique wise are you using a thumbs forward hold or holding your gun thumb high? I have the same problems sometimes with my 1911 - keeping the strong side thumb high can take pressure off the grip safety - that is one reason a lot of guns have the thicker metal pad built out on the bottom.   Hold the gun in one hand and watch how the grip safety moves as you raise and lower your strong hand thumb and you can see when you curl the thumb down it puts more presssure on the grip safety.

There's a spring that holds the grip safety bar forwards against the back of the trigger.  This works with a protrusion on the grip safety.  When the safety is engaged (no grip), the trigger pushes this bar backwards and it hits the grip safety protrusion, stopping the trigger.  Disengaging the safety (gripping the gun) pulls the protrusion upwards, out of the way of the protrusion, and the bar slides backwards into the grip safety when you pull the trigger.

Some things that come to mind.

- Grip safety isn't installed right or is defective.  It might not be pulling the protrusion fully out of the way of the bar.

- Spring could be weak.  If the spring is weak (or non-existent/destroyed) the bar might be in contact with the safety even when the trigger isn't being pulled, and gripping the safety could 'drag' the bar upwards with the protrusion.

Really the only way to tell is for you to take the grips off and see what is (or could be) going wrong.

NOT RIA problem, someone did not fit and reassemble your 1911 correctly after installing the other vendors parts.

read up on assemblying a 1911 and fitting a grip saftey.

Exactly! It wasn't fit properly and more than likely its a slight sear spring adjustment and your on your way or you may have to remove some material from the side of the safety.

ooops...didn't see that the trigger and grip safety were swapped out.  
in that case, whomever did the work didn't do it properly.

Here's some help.  Go to  the Fig. 9 & 10 area on this gunsmithing description from Blindhogg.com.  It gives a rundown on roughly what your problem is and how to fix it.