I have a roughed in basement bathroom with a 4 inch sewer line. I have no shower or sink drain.

Can I tie a shower and sink drain into the 4 inch sewer line?

Do I need a separate vent for the shower and sink?

What I was hoping to do is jack hammer around the 4 inch dig down far enough to put a pea trap then run my shower and sink drain from there.

I'm a rookie, any suggestions?

Sorry it took me so long to answer. I had surgery and I'm just getting back.

"What I was hoping to do is jack hammer around the 4 inch dig down far enough to put a pea trap then run my shower and sink drain from there."

No, You will cut in a 4" wye to pick up the toilet. Next you will cut in a 4 X 2" fitting to pick up up the lavatory. The shower will connect into the lavatory drain and be wet vented by it. From the 2 X 2 X 1 1/2" tee that you will stub out to pick up the lavatory you will continue out the top out the roof or revent back to a existing dry vent. This is the only vent you'll need if you lay it out this way. Good luck, Tom