Good one, stay off the A5 other than from Capel Curig to the Ogwen valley....if you go that way follow A5 down the valley towards Bethesda, take the left which brings you back up the valley but on the other side
You can make it out here...
Here's a nice very short one for you from Betws. Over the bridge by the falls.... bear right, follow until junction near Llanrwst go left up the hill and follow it all the way until just before (half a mile) the A5 at the Ugly cottage, left down the hill all the way back to Betws.
Look at your map there's great roads north of the A5 in the Pentrefoelas to Colwyn Bay area.....it goes on, you've seen Rocky's report including up by the Blue Lake above the Mawdach, there's loads to get you off the beaten track and hardly see any traffic.