The Knicks’ brain trust is about to look different. A valuable member of the group — senior vice president Gersson Rosas — is leaving the team after four years, culminating in the franchise’s first championship since 1973. President Leon Rose and executive vice president William Wesley get most of the credit from fans and the media for their roles in transforming the Knicks into champions. Having previously worked with the Timberwolves, he was a fan of Towns and his experience with that franchise helped the Knicks finalize the deal to acquire the floor-stretching big mn from Minnesota. Two years later, that trade — sending Julius Randle and Donte DiVincenzo to the Timberwolves — is an unquestioned Knicks success.