Roy, a regular at the top of the order in England's limited-overs sides, had been touted for a maiden Test call-up for the forthcoming tour to Sri Lanka but ultimately missed out.
Instead, once he and paceman Mark Wood have completed their obligations for the white-ball part of the trip to the island, they will link up with a Lions side containing the likes of Dom Bess, Sam Billings and the Overton twins.
Essex seamer Jamie Porter, who was perhaps unfortunate not to make his England debut this summer, is also part of the Lions' 15-man touring party for the four day 'Test' which will be played from November 18-21.
Highly-rated youngsters Matt Parkinson and Amar Virdi join Bess as the frontline spinners, while Worcestershire seamer Josh Tongue's call-up is subject to medical clearance after he suffered an injury in the County Championship this week.
Surrey wicketkeeper-batsman Ben Foakes is a conspicuous omission, with Billings, who captained Kent to promotion from Division Two this year, in contention to take the gloves.
Billings, Roy, Tongue and Virdi will drop out of the squad ahead of the white-ball leg of the tour to be replaced by Alex Davies, Lewis Gregory, Sam Hain and Saqib Mahmood.
The Lions will play five 50-over fixtures and two Twenty20s against the same opposition between November 25 and December 8.
England Lions squad for four-day 'Test': D Bess (Somerset), S Billings (Kent), J Clarke (Worcestershire), N Gubbins,(Middlesex), M Holden (Middlesex), T Kohler-Cadmore (Yorkshire), L Livingstone (Lancashire), C Overton (Somerset), J Overton (Somerset), M Parkinson (Lancashire), J Porter (Essex), J Roy (Surrey), J Tongue (Worcestershire), A Virdi (Surrey), M Wood (Durham).
England Lions limited-overs squad: D Bess (Somerset), J Clarke (Worcestershire), A Davies (Lancashire), L Gregory (Somerset), N Gubbins (Middlesex), S Hain (Warwickshire), M Holden (Middlesex), T Kohler-Cadmore (Yorkshire), L Livingstone (Lancashire), S Mahmood (Lancashire), C Overton (Somerset), J Overton (Somerset), M Parkinson (Lancashire), J Porter (Essex), M Wood (Durham).
