I don't think it will be possible to create a separate asset from it. For Lansweeper to create an asset itself, it needs to be able to connect to the device's IP address, and since the NIC is on a server, Lansweeper will simply scan the server. Additionally there would be no way of knowing what information to display on the asset since it's all seen as part of the server.
The best thing you can do is create a custom report which only displays the Drobo's information from the servers.