for roll over - I put morgan in a down position then had to giver her a little push with my hand to roll her over. When she completed the roll i gave her a treat. I did this over and over again with my hand for a couple minutes. Then i gave her the command and gave her a little push with one finger and she did it on her own. I did this for a few minutes. After she was rolling over practically on her own i stopped using my finger and added a hand signal with the verbal command. Now i can just use my hand signal and she rolls right over.
for come - i put her on a long leash. told her to sit and stay, walked to the end of the leash and then told her to come. If i had a treat she'd come right away. if i didn't she'd sit there like 'yeah right'. that's where the leash comes in play. gave her a little tug and had to reel her in. LOL after a few time of doing that she figured it would be easier to just walk over on her own.
now she does both with no problems. she's very smart and picks up on tricks within minutes. I taught her play dead in 5 minutes. Its easier if they already know roll over.
for play dead / BANG! - put her in a down position and used my hand to roll her as if we were doing 'roll over', but stopped her on her side, legs straight out and head down. Then said bang and stay to make her stay in that position. did this a few times until she understood to only half roll over. I also added the 'gun' hand signal. Now i just point my 'gun' at her and say bang or make a 'bang' sound and she flops right over and lays there. its hysterical.
good luck with your tricks and commands