Roll Over and Heel

Teaching our Sammy roll over was great fun - he picked up in a couple days.  What we did was make him lay down, then teach what we called "over" by gently pushing his shoulders to the side.  He likes to lay like that, and being part boxer does it all the time so he can have his paws free to bat at something, so it was easy.  He would actually stay over for several seconds for us.  Once he had "over" down we went for the last half - usually by moving my hand in a circular motion around his head and saying "roll" or "roll over", and catching his feet with my arm to help him roll all the way.  then of course treats and cuddles for doing it!!!  It isn't the easiest thing in the world for him, since he tends to twist, etc, so sometimes it takes him a bit to get from his back all the way over, but he's pretty good about it now. And he loves belly rubs, so being on his back is something he does often anyway. Now all we do is say roll over and move our hand in a circle around his head and he does it.  So cute!
 
Heel, on the other hand, I have little advice about - ours walks great on a loose leash until he sees a cat or squirrel, but we haven't gotten to working heel much since he often is SO good about it even if there's people nearby - its only those darn critters that set him off, and we dont see them often enough to get a lot of practice in.  and I didn't teach him to walk nice like that, it was a benefit of adopting a dog from the shelter. []

We did something similar to what Nicole mentioned with roll over.
 
When he is laying down, we push him over a bit at the shoulder.  He did not like this at first, but we kept practicing, and treating/praising like crazy.
We also moved our hand in a circular motion, and said "roll over".
 
Keep going like this, and eventually he will get it.
 
Now Tyson loves to roll over, and is really a pro.  He rolls over before we even tell him to, sometimes when we aren't even looking for a "roll over."  Its actually problematic sometimes!!

Get the dog to lie down and wait till she's relaxed (on one hip).  Get out a treat and stick it right on her nose - keeping it close to her body (shoulder), guide her nose around until she has to roll on her back to get the treat.  You can train it in increments if she won't roll all the way over right away (just don't say "roll over" until she finally does the complete behavior).

We taught Wes roll over by luring too.  He would lay down, and like Anne said, we waited until he settled on one hip, then got down and basically lured him over by bringing the treat around (very low to the ground right by the shoulder on the side that you want him to roll toward).  We said "roll over" as he was doing it and I don't think we actually ever had to push him over...  It is his favorit trick now and he offers it when he is in a down and trying to guess what we might want next - it is very cute!!

I'm glad there is more than one method to teach her this with. I'l retry the leading....she didn't go for it too much before. Thanks for the ideas!

Becareful when you teach roll over some dogs can get a twisted stomach and die within 2 hours!!!