The Rock is Christ. Anyone who falls upon this Rock will be broken and anyone on whom this Rock falls will be crushed. Christ is the only Rock, the foundation, and we are but little stones (rocks) who believe that He is the Christ, the Son of the Living God, builded up into the dwelling place of the Holy Spirit, the Church, the Body of Christ. God knows who we are. Christ knows who we are, and the Holy Spirit knows who we are. Peter knew who Christ was, just as we know who Christ is. It is that simple.
Only an RC could invent volumes of tradition around an invention called Pope and ascribe it all to that little verse, which is about Peter's profession, as everyone ELSE knows.