Is there a way that I can turn a character sheet into a monster stat block? I am trying to make some monsters, but there are sections for class and paragon path that are obviously meant for a PC. I have the D&D-4e sheet on.
Roll20 does not directly support monster stat blocks like this, unfortunately.
An alternative to just using the relevant portions of the character sheet is to use the 'Bio and Notes' section to load in the monster data, directly copy-pasted from the Compendium or your homebrew source(s) of choice. This requires pulling the pages up to look at the numbers, but is often faster than editing completed partial character sheets.
One tip if doing this: Keep the defense and passive values at the top, as they are on the monster stat blocks; this way, you can shrink the journal entry display window so it takes up less screen space.
Also, if DM'ing with multiple monitors, don't forget you can 'pop out' a block by clicking the double-window icon on the upper-left, letting you keep monster stats on a separate screen where they don't cover your battlemap.
I ran a few sessions of 4e DND on Roll 20 and I have no idea if you can actually make a specifically monster stat block in Roll 20 4e. I tried to find a monster sheet and I ended up specifically crafting monster sheets from the player sheet. the good news is that if you end up doing this you can ignore all the extra stats players have that monsters don't (stuff like Paragon Paths and Epic Destinies for example) you can fill out the monsters stats and powers exactly how you want to get the mechanical flow you want.
That being said, I was able to use it sucessfully to do this but it was a major pain, it wouldn't let me copy monsters automatically, I basically had to fill each individual one out the same way (if they happened to be duplicates)