It should be a 4 Amp 250V slo blow fuse. I think that it's 1 1/4 inch. If you take the original fuse out, and take it to the store, you should be able to match it up easily.
I did your homework for you because my fingertips are hurting and im bored. 4 amp slowblow fuse,,,,,,,look here on page 17
http://www.mesaboogie.com/manuals/Roadster.pdf
Heck yeah man, no need to be mean here. We're just a bunch of Mesaholics that like to help each other out. This site is awesome, and I'm proud to be a member of it.
I had a similar fuse problem for an american fuse,but I live in Scotland,a bit harder to find those fuses over her,this forum has excellent not only did one guy on here find me a place in the states that would ship them to me he offered to buy some and send them over to me
I found a bunch on fleebay and bought 50 of them for all in with shipping $15,thats me in fuse heaven