yes, that is a DL1 roadster, with 28 x 1-1/2" wheels. the ISO sizing for this tire is 40-635. based on the details of the bike in your photo, i would peg the year between 1970 and 1972.

you can readily find tires in this size, and my favorite is the schwalbe delta cruiser, in creme. here's a picture of my DL1 with those tires, taken yesterday: