Rossi already has experience with the team, having taken part in the first free practice session at the Canadian Grand Prix, while this will be Stevens' first outing in an F1 car.
The pair will drive on the opening two days of the test, with Charles Pic and Giedo van der Garde running for half a day each on Friday.
Stevens, who is a frontrunner in Formula Renault 3.5, said: "I spent quite a bit of time last week in the simulator so I'm comfortable with most of the systems I'll be working with and, while obviously nothing can really prepare you for the first time you drive an F1 car, I'm as ready as I can be."
Silverstone test line-up as announced by teams so far:
* The driving schedule will be confirmed each morning