I have been on many trips as a solo traveler without a roommate and have had mixed experiences. On a recent trip as the only one without a partner I was frequently asked to change my place at the table so couples could sit together, and I would get moved down to the far end of the table. With other groups though, if I offered to move I was reassured it wasn't necessary as they didn't need to sit together all the time. Groups have different temperaments. Another time several of the hotels had tables set up for exactly four people and I was pretty much excluded from this set up. Or the dinner on your own would occur after a free afternoon or siesta time so I was alone because couples, (including) roommates made their plans when I wasn't around so I had no way to ask or be asked to join anyone. One time we were so many single women that a consensus was never reached and we just had pizza in the hotel.
I want to emphasize that uncomfortable situations have been the exception, but I always know that they may arise, and I certainly won't let such occurrences spoil my trip. But also, before choosing a trip, I check how many dinners are not included, and this is part of my decision. Occasionally I travel with all women, not with Road Scholar, and there the group leader usually suggests a place, and most people including the leader go together. But in my experience Road Scholar leaders generally are not around when plans are being made and are not involved in the process.
Other than meals, almost everything is done as a group, and the group is usually together just before the free times, so plans can be made with others. So I may set out with others, but often prefer to go at my own pace and follow my own interests. Still I never hesitate to travel with Road Scholar as the problems I mentioned are definitely the exception.