Rovers, winners of the competition in 2002, have made it to the last 16 thanks to wins at Gillingham and Nottingham Forest in the second and third round respectively.
The match will be held during the week commencing October 26.
Chelsea seem to be in the picture to collect Argentine striker Mauro Icardi in the summer from Inter Milan as
According to reports, Chelsea are in talks with Atletico Madrid to sign the 23-year-old Spanish midfielder commonly known as Koke.
Watford may have been denied the Championship title in the last few minutes of a dramatic season, but there has
James Tavernier has made a big impression at Ashton Gate since joining League One champions Bristol City on loan from Wigan in January.
The 20-year-old striker has been in the news recently with speculation the Serbian could be joining a Premier League club