Welcome CapriCasino!

There are a few main reasons why Roth wanted Mike dead. Firstly, Mike ordered the hit on Moe Greene, who was Roth's best mate (remember him screwing at Mike in Cuba about not asking who ordered the hit on Moe?). Secondely, since Michael took over the family buisness and moved out to Nevada, he has moved in on plenty of casinos owned by Roth, so thats why Roth felt threatened and wanted Mike dead, cause he was muscling in on his buisness.

Roth used the 2mill as a way to get close to Mike, the deal was not actualy gonna go threw,as Roth assumed Mike would be whacked before. Roth just wanted to get close to Mike and used this 'deal' to do so so he could kill him.

Finally, the hit on Frankie by the Rosato brothers,(who were backed by Roth). I believe that the Rosato brothers said this just in case Frankie survived, so that he would nt come back at them and Roth, but Frankie would believed it was Michael who ordered the hit, who, if you remembered had a disagreement with Frankie at the beginning of the film about the Rosato brothers. Therfore Frankie would be obviously a little p*ssed off at Mike, and so testify in court against him,later on. Therefore Mike would be put away and Roth would not have to worry bout him. Im not 100% on that though so you mite need a little more help on it!

hope i helped geezer.