I personally think the first 6 months are more relaxing and boring (except when you first come from the hospital and have to breast feed a crying baby every 2 hours). After 6 months, things start picking up, the child is more fun, yet there's a lot more work and involvement.
I don't think my son started rolling over until 3/4 months (it's hard to remember now, but it was monumental!). It takes a while, too, because first they learn to roll onto their side. They like playing on their side and stay in that position for awhile. Then they pump and kick their legs to get back in their original position or roll over another 90 degrees.
So don't worry, your daughter is still with the average if she's not rolling over at 2 months! After rolling over comes the propping up on pillows in a sitting position stage.
If you're interested in what stages your child should be at each month, try the book "What to Expect the First Four Years." It breaks down which point your child should be at each month for the first year. You can also apply to some free e-mails from Enfamil.com. I don't know how I got on their list, but they sent me free formula samples, coupons, and monthly newsletters.