Roscommon are a team on the up but captain Niall Carty knows that they will pay dearly if they fail to take the challenge of London seriously.
The Rossies won the Division 2 crown last month having won promotion from the third tier the previous season.
They are favourites to reach a Connacht SFC final, with Sligo waiting in the semi-final for the winners of today's tie (3pm).
But, having beaten the Yeats County and Leitrim in recent years, Carty knows that Paul Coggins' London are capable of an upset.
“If you look over the last few years, London have turned teams over, over in London,” Carty told RTÉ Sport.
“We can’t get complacent, we can’t look too far ahead. We’re fully focused on that game.
"There have been a few lads who have been over there, be it league or championship, over the last few years so we know what to expect.”
"John’s fantastic, he’s the most enthusiastic man about football that I’ve ever met"
The full-back went on the praise manager John Evans for taking the team to the next level.
He said: “John is fantastic, he’s the most enthusiastic man about football that I have ever met, and it rubs off on you, it rubs off on the all the lads.
“You can see that on the field during games, in training sessions, there’s a great buzz around the place and that’s what he brings.”
