Wood magazine a long time ago had an article on router table turning. I guess you could do a pool cue that way, but it would be a little tricky. The first thing you would need to do is create two circles of different diameters. The circles are then put on each end of your stock. You then build a box to hold it, with a back, 2 sides and a bottom. This gives your circles something to ride on. A slot in the bottom of the box allows the box to slide over a bowl bottom bit. As you roll the stock over the bit it turns the square stock round, and as you slide the box left and right, that creates a tapered cylinder.
Even breaking a pool cue down into two pieces, it might be a little cumbersome to do on the router.
Hope this helps,