Fake American: Charlie is played by Welsh actor Damien Lewis
English, not Welsh, and an old Etonian to boot.
Hey, It's That Guy! - Roman is played by Garret Dillahunt, the actor who plays Cromartie on The Sarah Connor Chronicles. In a minor variant, he appeared on Life before SCC even started, and returned for season 2. Dani is also the very first ghost on Supernatural.
There must have been some connection between Life and Deadwood. Besides Dillahunt, who played two characters on Deadwood, there was Brent Sexton (Bobby Stark on Life, Harry Manning on Deadwood), Robin Weigert (Karen Davis on Life, Calamity Jane on Deadwood), and Titus Welliver (Kyle Hollis on Life, Silas Adams on Deadwood), as well as William Sanderson (who played E.B. Farnum on Deadwood) in a guest part. Almost all were prominent characters on both shows.
Someone had to have recognized the titular character as Major Winters. Skip Muck (who is also Gabriel) and Bull Randlemann turn up too.