For dice rollers you can always use the [url=http://www.wizards.com/dnd/dice/dice.htm]Wizards of the Coast Dice Roller[/url].

There is also [url=http://invisiblecastle.com/]Invisible Castle[/url], for when the honor system isn't good enough.

Roll20 does have its own rolling engines, which can include random number generation, or physical dice simulation. It includes powerful formula capabilities to leverage, which can make rolling easy and simple. It even features a GUI to make it reeeal simple instead of having ot  slap together algebra-like code. And like Invisible Castle, it logs the rolls, though it's not as easy to post each roll separately. 

Another option is using the randombetween function in a spreadsheet such as Google Docs, or Excel, or even Open Office's spreadsheet functions. 
Though this is kind of a pain in the neck, and is less user-friendly.