The word came to prominence in playgrounds from the mid-1990s and is usually qualified by the word ‘total’ as in “that guy’s a total roaster” but arguably absolute does the job just as well and usually hits the mark.
It is used to describe an individual or a group generally making a show of themselves. “Did you see that roaster oan the X-Factor?” is one example.
Roasters are first cousins of rockets although being a total rocket is probably worse than being an absolute roaster – unless you were playing Scottish slang words Top Trumps then any kind of rocket would likely score you higher. Arguably, roaster can also be used as a harsh or humorous critique with the intention of paying someone a cheeky compliment.
However, this time it’s the councillor who’s been left feeling the heat.