Pretty sure that a second season was planned at the time season one ended.
Err: RD != R. Dorothy. Though, it does reaise the question of whether RD is just another incarnation of R. Dorothy in a different dimension, universe, simulation, etc.
There is always some degree of sexual tension between R. Dorothy and Roger Smith, just like there is between Angel and Roger Smith. It also shows that R. Dorothy knows somebody else has been around, and gives info as to who that person is.
Ah yes, the Doomsday device.