You need to find the missing coins first. Then, your phone will ring and go to G. He will tell you what you need to do on the rooftop.
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the last key to the the left
you dont :)
in the nightclub
it is in the HQ next to where G is
try getting it
just drag the key to the door and click and let go
Go to the vault and click on the coins and Rookie will pop up and will talk to you.
You give it to G he's in the headquataurs
0466 going clokwise
In G's droor
u ive it to g so he can investagate