Don't do this in wooded areas. Fire can travel underground through the roots, and set nearby trees on fire. Roots can burn very slowly, so the problem might not be apparent until days or even weeks later. I would also recommend that you avoid doing this if the roots might have entangled with an ancient gas line or other buried utility lines. Roots tend to burn extra well if you have let the stump dry out for a year or two, but this is a danger even with freshly-cut trees.
There are alternatives; you can try to pull it out, using strong oxen or a tractor, or you can drill some holes in it and leave it to rot out in its own time. Many people will scoop out enough of the heartwood to use them as low planters for flowers, which prettifies them and increases the rate of rot.