Not long before I saw it, I'd hear it make short buzzing sounds periodically. When I finally saw it, it was sitting on my desk and then began flying (somewhat clumsily, more like a bee than a housefly) toward/around a light I just turned on. I was scared so I ran out of my room and came back 20 minutes later but I couldn't find it anywhere. So, I turned out my lights and came back after like 15 minutes and I saw it walking across my floor! So I sprayed it with hair spray and slightly stomped it.
I attached a photo of it. Its a very dark brown color but my camera flash and the hairspray kind of distored the color shown. I feel like it resembles a cockroach but I've never seen one in person. The fact that it flies, buzzes, and is attracted to light has me puzz
These are now the remains of a Western Conifer Seed Bug, Leptoglossus occidentalis. This I'd a North American bug that is colonising Europe, including the UK, through accidental introduction with trade. It is now residential and breeding in the UK but many are flying in from mainland Europe and as you say are attracted to lights at night.
They are harmless - if you see any more just chuck them outside where they would much rather be.