Uncleaned ancient Roman coins attract a lot of attention from collectors who would prefer dealers (and other often well-intentioned souls) not damage coins by trying to clean them too much. Most uncleaned ancient Roman coins can actually command higher prices than their more sparkly but less complete brethren.
Collectors have different reasons for focusing on uncleaned coins when adding to their own collections. You may want to embark on a cleaning project yourself with such coins, or you can leave them as is and make their wear and grime part of the fun. It’s up to you… but remember it’s usually best to err on the side of keeping the original coin intact, if a little grungy.