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I use the roller specifically to train my balance and riding skills when I can't get out on the road. So having a bracket or something would defeat the purpose for me. In spite of my position here, your idea is interesting and I am sure you would find buyers if you put it on the market, especially if it could be used with all brands of rollers (i.e. not attached directly to the roller frame).

Kreitler offers a fork stand for their roller, as does Tacx. However, I think they hold the bike still as opposed to your concept with some movement allowed.