There's no high level tool to do this, but you can use the geometry engine to work something out.
If a road in this case is a polyline, you can find the distance between the road and the point, and if the distance is less than some number, move the point onto the polyline. Here's a simple example showing this: JS Bin - Collaborative JavaScript Debugging (mouse over the view around the line to see the snapping effect)
A few things to note: I recommend doing all of this in the web mercator spatial reference. Whichever spatial reference you use needs to match, that is the polyline's sr must match the point's sr. In the example, I set the "snap distance" to 10 pixels. If you want to snap based on world-meter-distance, you could take out the pixel logic and use meters instead.
