Williams signed a deal with the Wizards on Friday, according to NBA reporter Chris Haynes.
Essengue enters his second NBA season after spending much of his rookie year recovering from shoulder surgery.
Okoro remains primarily a defense-first wing heading into his second season with Chicago.
Watkins (knee) didn't play in Saturday's 91-83 Summer League win over the Hawks.
Beekman registered 13 points (5-10 FG, 1-3 3Pt, 1-1 FT), six rebounds, 14 assists and one steal over 31 minutes in Saturday's 91-83 Las Vegas Summer League win over the Hawks.
Okpara posted 12 points (6-13 FG, 0-1 3Pt), eight rebounds, two assists and one block across 27 minutes in Saturday's 91-83 Summer League win over the Hawks.
Sellers accumulated 17 points (6-12 FG, 3-8 3Pt, 1-1 FT), two rebounds, one assist and two steals over 26 minutes during Friday's 100-91 Las Vegas Summer League loss to the Cavs.
Atwell logged 22 points (8-10 FG, 6-7 3Pt), two rebounds, one assist and two blocks over 27 minutes during Friday's 100-91 Summer League loss to the Cavaliers.
Wilson (rest) is out for Friday's Las Vegas Summer League finale versus the Cavs, K.C. Johnson of Chicago Sports Network reports.
Swain is out for Friday's Summer League game against the Cavaliers due to right wrist soreness, per K.C. Johnson of Chicago Sports Network.
