Is there a way to determine if a DGN file was created in either MicroStation or OpenRoads without opening the actual file?

Search your C:\Program Files\Bentley\...  OpenRoads directory for CivilFileManager.exe. This is an app delivered with OpenRoads that can load a file, folder, or folder tree and manage some of the Civil data. A plain MicroStation file will not have an Civil data, while an ORD file will.

That's about the only way I know. Both software natively uses DGN format, and there's no real way that I know of to tell you what was used to create it except checking for the presence of civil data.

It is possible that, if you open an ORD drawing in MicroStation, you might get some type of warning.
Unfortunately, there is no such warning when opening "plain" DGNs in ORD.