Why is roland seeking the dark tower?

In the beginning of Steven King's "Dark Tower Trilogy," Roland Deschain is determined to reach the Dark Tower, climb to its top and questions the gods who live there about the state of the world. Ultimately, however, before the end is revealed, it becomes clear that Roland is possessed of the belief that once he gains access to the secrets that the tower holds, he can set the world to rights, and perhaps save himself in the process.