On this point I'm with the Roth of the GFII second draft. In this version, when Michael visits Roth and pretends that it was Pentangelli who tried to have him killed, and then goes on to say that Frankie is a dead man and will thus need a replacement, Roth says:

"Michael, these things are unimportant. Who should be the manager of a dime store, Joe or Jack? Unimportant. You do what you think is right."

Roth and Michael are on a higher tier of business operations, which makes the New York crime scene look like a nickel and dime store. It needs to be attended to, but in the grand scheme of their higher level dealings, the New York people are "small time enforcers," to borrow Michael's description of Zasa in GFIII.