From Ocracoke Island -
Take the ferry to Swan Quarter (not Cedar Island)
Continue north on NC 94 to Columbia
To Phelps Lake, Somerset Plantation
To Edenton then Merchants Millpond
To Franklin, VA, Courtland, Jarratt, to Alberta
To Victoria and VA 40 across southern VA to Rocky Mount
To Blue Ridge Parkway west of Ferrum past Fancy Gap
To Galax and then down the New River Trail to Draper
From Draper there are nice back roads into Roanoke.
The problem with North Carolina is the massive growth of the Piedmont metro areas -
Raleigh-Durham, Greensboro-Winston-Salem, Charlotte.
They form a near wall of poor roads with heavy traffic.
There are bike maps from the NC DOT -
But I really wouldn't rec the Mountains to Sea any more because of the metro areas.
The North Line Trace is a better option if you wish to stay in NC.
I think the maps are still free - but they take a while to arrive.
Plus by the end of summer they are often out - call ahead.
If you start with my route from Ocracoke, you can connect with the NC North Line route - Bike Route #4.
Not guaranteed, but the route is pretty well marked with signs like this at every turn.