Hello Simon,
I think it exists no (public available) x64 version of SAP ROT wrapper. But I know it is possible to use x86 COM libraries in x64 environments. You can find an example how to do register the libraries correct in the comments of this post, it is for another library but the way is the same. You can see here that it works. How to access it via dotNET you can find here, in this example via PowerShell. On this way you can connect SAP GUI Scripting API to get the information about the SAP environment, client and transaction you need.
Let us know your results.
Cheers
Stefan