Roth had already arranged for Michael to be assassinated in a military car but the contract money has not been paid awaiting the all-important $2M

Roth was slippin'.... if he thought he was still going to get the money after his soliloquy

I reckon the assassination was going ahead with or without the $2 million No doubt it would have been worth it for Roth even if he had to pay his own money but no Bonus!
However he showed his hand with his Plan A warning bells otherwise he would have never suspected and been a sitting duck in Roth's Havana