Several points:

• The third byte of your messages is "01". However, the MIDI implementation document of the VT-4 states that "10H" is the default. The correct value depends on the "Device ID" (or whatever it's called exactly) of the receiving device: if these values don't match, your VT-4 won't react at all. If the VT-4 functions like most other Roland devices I've seen, the default "10H" will be shown on the device as "17", i.e. the decimal representation of 16(=10H) + 1.
• Both your messages contain "51H", which should be "51". (This is just a typo, but still...)
• Any SysEx message needs to be terminated by "F7".
• Any Roland DT1 message needs a checksum byte immediately before "F7".

MIDI Tools has a dialog box in which you can construct full Roland DT1 messages; most importantly, the dialog box automatically calculates the correct checksum.
You can open this dialog box from the "MIDI System Exclusive messages" window via Edit -> "Insert Roland" or via the "R" toolbutton.
In this dialog box, you need to set the value for "Device" to the decimal value shown on the device, i.e. probably 1 higher than the internal value. So for the VT-4's default "10H" you need to set "Device" to "17".
For "Model" the VT-4 needs "00 00 00 51".
Address/size length = "4"
Command = DT1
Address = e.g. "10 00 00 05" (Monitor Mode)
Data = e.g. "00"
For the above values, the dialog box generates the following message:
F0 41 10 00 00 00 51 12 10 00 00 05 00 6B F7

Hope this helps,
   Mark.