All I can say is that they DO grow out of it, and at four months you don't have too long to go. I remember the snarling and rolling on the back. I don't think it's 'answering back' as such. Cockers are quite sensitive. I can't tell Henry off by raising my voice - he backs up, growls or barks, butt in the air, head low. He's not being aggressive, he's upset. Took me a while to realise this (not that I shouted at him often, but puppies do sometimes drive you insane!).
The rolling on the floor and growling with biting sounds like he's trying to initiate play. It's a frustrating age - for him as well as you - when he finds it hard to entertain himself and doesn't understand why you aren't always ready or available to play. A quick time out in the garden is something I used to do too, just to let everyone calm down. And persist with redirecting play to things other than your person! Our best toys at this age were really long tuggy toys. Played with gently, it gives him something he's allowed to bite and play growl at, and saves your hands.