Tannhauser Industries (lab)
Caitlin's mother Dr. Tannhauser runs some tests on her cold powers in episode 3x05 “Monster”.
Barry and Wally go to stop Ramsey Deacon but he manages to take control of Barry's fancy new suit in episode 4x02 “Mixed Signals”.
Moretti Brothers' Warehouse
Vanessa Jansen crushes Bobby Moretti into a tiny cube and steals his guns. Nora shows up when Barry is investigating the scene and he has to pass her off as his new intern to Captain Singh in episode 5x02 “Blocked”.
Cicada changes into his work clothes and thinks back to the murder of Gridlock earlier in the evening in episode 5x02 “Blocked”.
The new Rogues infiltrate the secure weapons testing lab but the others turn on Nora and hold her hostage to draw out the Flash in episode 5x20 “Gone Rogue”. Nash guides Barry and Cisco to the vault where the cure-all syrum is stored in episode 6x04 “There Will Be Blood”.
Gun Smugglers' Warehouse
The other members of the gang run by the smuggler Ramsey killed are attacked at night by their dead boss in episode 6x03 “Dead Man Running”.
Frost and Barry try to stop Mitch Romero when he attacks another lab but they learn he cannot be killed when Frost throws him out a window in episode 6x03 “Dead Man Running”.
Rachel Rosso's Office
Ramsey remembers his mother when he learned that she was sick in episode 6x04 “There Will Be Blood”.