Oswalt isn't currently in the MLB and probably won't be for a few more weeks (Averaging 3 innings per start in three minor league starts so far while sporting a 7.71 ERA), so he'd be the easiest choice right now, though I'm sure another manager would snap him up immediately.
I don't think you can drop Vogelsong the way he's pitched last year and so far this year. Mediocre K/9 or not, he's valuable right now.
I think Latos is due for some improvement, but I don't think it will be much... He's been a fly ball pitcher his whole career and fly balls + Great American Ballpark = lots of HR's. You can get away with a 42% fly ball percentage in San Diego, but you definitely can't in Cincinnati; his HR/FB rate has literally doubled, and while it may come down a little bit, it's certainly going to stay considerably higher than it has been in the past. I think that's the main reason for his struggles... If he acclimates to the change and becomes comfortable with a different approach on the mound, he should be fine. He's given up 13 HR's already this year after giving up 16 last year. Huge difference.
I'd drop Samardzja if you want one of those releivers; what's he going to do that you can't replace somewhere down the line if you need to?
12 Team H2H, 4 unrestricted keepers
C - Mike Napoli
1B - Eric Hosmer
2B - Jedd Gyorko
3B - Todd Frazier
SS - Jhonny Peralta
OF - Ryan Braun
OF - Mike Trout
OF - Shin-Soo Choo
UTL - Brett Lawrie
UTL - Adam LaRoche
Bench - Austin Jackson
DL - Aaron Hill Hanley Ramirez
SP - Clayton Kershaw, Madison Bumgarner, Ubaldo Jimenez, Jhoulys Chacin, Ervin Santana
RP - Glen Perkins, Heath Bell, Jose Veras, Ernesto Fireri, Edward Mujica, Carlos Marmol, J.J. Putz
RCL - Cracking the WHIP - Admiral Trey
C - Yadier Molina
1B - Albert Pujols
2B - Jose Altuve
3B - Jedd Gyorko
SS - Jimmy Rollins
MI - Everth Cabrera
CI - Justin Morneau
OF - Jason Heyward, Shin-Soo Choo, Michael Morse, Nick Swisher, Ben Revere
UTL - Kendrys Morales
Bench - Garrett Jones, David Freese
SP - Justin Verlander, Cliff Lee, Ryan Dempster, Ubaldo Jimenez
RP - Jonathan Papelbon, John Axford, Glen Perkins, Ryan Cook, David Robertson