That pick is reportedly a conditional seventh-rounder in 2020, a source told Justin Rogers of The Detroit News.
Roberts, a fourth-round selection by the Lions in 2017, caught 13 passes for 146 yards and three touchdowns in his first two seasons. He played in eight games last year before a shoulder injury ended his campaign prematurely.
Meanwhile, New England continues to cast a wide net to build up its tight end depth following the retirement of star Rob Gronkowski.
Veteran Benjamin Watson, who was signed out of retirement, is suspended for the first four games. Austin Seferian-Jenkins was also brought in, but the Patriots released him earlier in June due to personal reasons.