Basically what you do for street roulette is to walk in a city with streetlights, going only in the direction of the walk light until you reach a place that looks like it would be fun.
For example, let's say you start at Bleecker and Macdougal. Follow the route with the walk sign. This should enable you to go in zig zags and you can end up at Central Park, The Plaza, Grey Dog's Coffee, etc.
I played street roulette for two hours and only ended up at a Starbucks.