MLB.com had ranked the 20-year-old Lugo as the 12th-best prospect in the Blue Jays system. He hit a combined .257 for Class A Lansing and Class A Advanced Dunedin.
Romack, 29, was hitting .289 with 33 doubles, 22 homers and 87 RBIs for Reno this year. His 26 RBIs during the month of July were the most in a single month in team history.
Hessler, 26, was 4-2 with a 1.68 ERA combined for Class A Visalia, Double-A Mobile and Reno. He will take the spot vacated by left-handed reliever Oliver Perez, who was dealt to the Astros on Friday night.