welcome to the board. There are some folks here who really can tell tou how to introduce the 2 dogs togeather . To use a bad point, but how would your wife act if suddenly you walked in and said here is my new wife we are all going to live here to geather. Same type of thing Rocco has always had you alone now you want him to accept this new comer as if nothing has changed . He doesn't see it that way.
As I said there are some who can explain how to introduce them so it'a non threaten to Him.