Hi,
When you connect any MIDI Device to Cubase, Cubase sends the
F0 7F 7F 01 01 60 00 11 1D F7
SysEx Message. This message asks the device “What kind of device you are?”. The device should sends another SysEx Message with providing the vendor ID and the model ID.
This is where are my thoughts going to. Could this communication between Cubase and Roland block the startup?
How is your Preferences > MIDI > MIDI Filter set up? Do you filter SysEx messages or not, please?