Yes the Romans, and Greeks, used spying and espionage frequently before assaulting a city. These spy's would assassinate military leaders, sabotage scorpios, catapults and onagers, poison wells, recon(map out weaknesses and detail defense movements) and causing outright havoc.

The Romans also participated in political espionage. Spy's would ask tribes around the regions they were in( either to take the tribe for resources, or ask for help) and ask if they would join them, if the tribe said no, the Romans would know they were hostel and eliminate them. These spies eavesdropped on neighboring cities political forums and public market places for vital military information. These secret spy forces were so good they discovered conspirators in the assassination of Caesar before he was betrayed, unfortunately, the intelligence was ignored and Caesar was stabbed something like 23 times in the chest.

The art of espionage and spying was alive and vital even with the Mesopotamians because if it's valued output. The Romans and Greeks were arguable the most elite in the ancient world, this was one if the reasons why the story if the Trojan horse was made, to make a statement of the Greek intelligence's superiority. And Rome, ever expanding needed as much information as possible on its enemies and friends alike.