The very obvious first suggestion is the Antrim coast road which is best ridden mid-week when it is much quieter.
The Glenelly Valley Road (B47) between Draperstown and Plumbridge runs through the Sperrin mountains and there are lots of little roads off it to explore. A very scenic route and largely overlooked which will suit you just fine.
For example, starting in Garvagh go to Draperstown, Plumbridge, Gortin, Omagh, Cookstown, Portglenone and back to Garvagh via Kilrea. 110 miles and a nice wee appetiser.