around the 1930's
FIXED: Presuming Rory said 50 years before he was born as is about the same age as Amy, who was 7 in 1996, they were both born in 1989. Now, 50 years before he was born, means that they were both transported to the year1938-1939, and since they are both around 31-32 at this point and Rory lives to 82, which is 50-51 plus years older, Rory probably died in 1990-1991. Amy probably died in 1995-1996, around the same time the 11th Doctor crashed in her garden for the first time, but we can never know, this is all a presumption. Hope this helps.
Update: Just to clarify the sourcing on the above. Today (Oct. 12/12) the BBC released a mini-episode (actually a scene cut from either Power of Three or Angels Take Manhattan) that says Rory was sent back "at least" 50 years before he was born. I say at least because the dialogue indicates that as of when he wrote the letter to his father, but in fact he says he waited a number of years - until after 1946 when he and Amy adopted Anthony - to write the letter, so in fact they might still have ended up in the late 1930s. The mini-episode has been posted to the BBC's Doctor Who website and is on YouTube. It's title is P.S., written by Chris Chibnall.