Nick Martinez is the #5 starter, Tanner Scheppers is the Opening Day starter, Pedro Figueroa is in the bullpen, and Tommy Hanson has been released, among many moves and announcements the Rangers have announced.
Evan Grant has a blog post detailing all the moves, which also include the fact that Scott Baker has been signed to a minor league deal, infielder Donnie Murphy has been claimed on waivers for the Cubs, and Seth Rosin (a Rule 5 pick) has been claimed on waivers from the Dodgers.
The rotation, per Grant, will be Tanner Scheppers, Martin Perez, Robbie Ross, Joe Saunders, and Nick Martinez, with Joakim Soria, Alexi Ogando, Neal Cotts, Jason Frasor, and Pedro Figueroa are in the bullpen. There are two spots still open in the bullpen.
I'm going to do individual posts about the most significant of these moves, which will be going up over the course of the afternoon.