She's still only 5 months the little cherub!
If it makes you feel any better, my DD didn't say her first word until 7 months (dadadadada ), and now she just won't STOP!! hahaha, she is constantly chatting away, she has begun stringing words together (probably started that areound 13 months) such as "whats that", "hey, there he is", "no don't want to" (she is now 20 months, and she is the only one in mums group that has really taken off with her talking). So i definately wouldn't worry about the talking.

Also my bestfriends little girl is 5 months and she hasn't rolled yet either, yet she is a healthy beautiful little girl, i really wouldn't say that there is anything at all wrong with her.

I'm sure she will do things in her own time, we all do! Also RE: tummy time - i don't think many babies enjoy it! heehehe

Goodluck! I hope this makes you feel a little better