Not a teacher only a native speaker.
I was going to answer with a short one line answer, but the more I thought about it, the more I realised it wasn't as simple as I first thought.
It could be used in this circumstance, however, I would associate 'roaming' to be more like drifting aimlessly, not knowing where you might end up.
If you have a set agenda and know where you are going eg. If you were walking in London and wanted to see Big Ben, the London Eye and Buckingham palace, then I wouldn't say you were roaming.
Although, I would say roaming would be acceptable if you were in London sightseeing, but didn't mind what you saw or had no particular agenda, you were just wandering around hoping to see something interesting.
I hope this helps, please let me know if you don't understand.
- For Teachers