Clue: Fiddler occupying one roof (4)
Answer: NERO
Explanation: Definition: Fiddler
A hidden answer ('occupying') in 'o**NE RO**of'. According to the legend, Nero played th fiddle during the Great Fire of Rome in 64AD, which would have been very clever of him, since the fiddle was not invented until the best part of a milennium later (lyre, maybe, but it is by no means certain that Nero was even in Rome at the time).