Bryan Donovan is an older man, having worked in a police station in some middle of nowhere town for who knows how long. While he's content with the passive lifestyle he leads, it'd be bold to assume he isn't ready for whatever challenges he faces. In terms of voice, I think the best points of reference would be actors like Bryan Cranston and David Harbour: voices that sound a bit older, but clearly indicate they're out completely out of their prime just yet. Bryan Donovan will be a very important recurring character throughout the series.