He, however, clarified that the former Rajya Sabha MP or for that matter any individual was not more important than the party.
Addressing district-level party leaders at a meeting in Siliguri, the state BJP chief said: "The BJP would benefit if Roy joins the party. But he is not a factor for the party as he was for the TMC."
Anybody who joins the BJP would have to follow certain rules and regulations, he added.
Mr Ghosh had on a previous occasion lauded Mr Roy as a "good organiser" and said he had made a "big contribution" to the growth of the TMC in Bengal.
The indication that Mr Roy was likely to join the BJP came when organisers of the BJP national secretary Rahul Sinha's birthday party on October 25, invited him.
Mr Roy, who was once the second-in-command in the TMC after its chief Mamata Banerjee, this month resigned from the Rajya Sabha and quit the party.
He had described the BJP as a non-communal party and said that the TMC would not have tasted success without the backing of the BJP at the national level during its initial years.
The TMC suspended him for six years alleging that he had indulged in "anti-party activities" as soon as he announced that he would quit the party.
Mr Ghosh also claimed that with the BJP becoming the main opposition party in West Bengal, the TMC was allegedly pursuing "vendetta politics".
BJP workers were being arrested on "false" charges and killed, he said.The BJP leader also asserted that his party would form the next government in the state.