The Metzlers are good tires. Were you satisfied with the ride and grip?
Did they turn in OK? Did they last a long time? Did they wear evenly?
The Bridgestone BT-023s are another good alternate choice for the Roadster. The standard BT-023 tires should give you good feedback and wear. The GT spec is not really necessary unless you ride with a passenger a lot, tour with really heavy lugggage, or weigh 290 pounds
and ride at very high speeds. They are designed for slightly heavier bikes.
Bridgestone' new S-20 is out now, and grips very well. Jury is still out on how long they will last.
Also, the new P3s by Michelin. These tires are extremely popular, and for good reason. They have a great balance of high grip and long wear characteristics. Michelin makes excellent tires.
Dunlop has a Roadsmart tire that is also another choice. If you ride like you are touring, it is a very stable tire. Good grip and long lasting. Mine did not give as much feedback as the Bridgestone BT-021s, but lasted almost as long. If you ride more like a sport rider, Dunlop's Qualifier series may suit you better. More grip, less life.
Pirelli has an Angel and other good tires for our Roadsters.
Continental tires come standard on many new BMWs now.
I am not a tire expert. Read the reviews, talk to other riders, and think about the way you'll be riding, and what expectations you have before buying new tires. It may come down to what you find the best deal on.