I have read that you should look for an actual drum monitor (one that was designed for use with drums) because there are certain high and low ranges that other monitors don’t have. I bought this one off Amazon and couldn’t be happier:
I don’t have the same Roland (I recently got a TD-1dmk) but got one of these:
Donner DDA-35 AMP 35-Watt Electronic Drum Amplifier Keyboard Amplifier
Since I’m new to this I don’t know if this is a good or bad amp. All I know is that it sounds good, is pretty loud for home use (I can make the whole house shake from the basement) and I can also plug our Yamaha electric piano into it. Plus, it was less than $200. I was tired of showing off my drums and the only thing people could hear was the sound of the sticks on the pads. Now it sounds like a proper drum kit, and I’m looking forward to playing along with our 16 year old on guitar.