Okay, so the Astros acquired the following players today (alphabetically);
They also traded the following players away (alphabetically)
Derek Fisher (40-Man)
Corbin Martin (40-Man)
Max Stassi (Active & 40-Man)
How does the Active Roster / 40-Man Roster fit with all of this going on?
First off, you do not need to put Rivas, Stevenson, or Uceta on the 40-Man Roster. So the Astros cleared one spot on the Active Roster (Stassi) and three spots on the 40-Man Roster (Stassi, Fisher, Martin).
According to the current Active Roster on the Astros' website, there are only 24 listed and that's with Marisnick sitting out tonight's game, putting the Astros' active roster at 23. (UPDATE: Bryan Abreu is the 25th guy). Then you subtract Stassi, and you have two spots. I think those three spots go to Greinke (just a hunch), Biagini, and Maldonado. This is assuming that Sanchez gets sent to Triple-A, but if not then he takes one of Abreu/Urquidy's spots on the Active Roster.
The 40-Man Roster is a little more complicated. McCullers is already on the 60-Day IL, so he doesn't count for a spot. There were 39 on the 40-Man but Fisher and Martin get removed thanks to the trade. Maldonado, again, replaces Stassi. So that's 37 on the 40-Man, leaving three spots. Greinke, Biagini, and Sanchez get those three spots to bring it to 40. Voila.
When Peacock, James, and Pressly come back, it's pretty much a slam dunk that Cy Sneed and Jose Urquidy go back to Round Rock. Then, since you're really adding three pitchers, you have to wonder about the safety of Hector Rondon.