This post covers the basics of symbol rotation in ArcGIS Online web maps. Symbol rotation is easy, and is perfect for "direction focused" point features. These include cameras, travel direction, wind direction, and much more.
But there are some very interesting things you can do using a combination of stacked symbols and rotation, covered in this post:
Stacking symbols allows you to create gauges, that rotate with your data whether it be static or live.
This post covers everything above, with a sprinkle of Arcade thrown in. Arcade is used to calculate the offsets needed to rotate the needle on top of non-circular, or non-half-circular gauges.
Using these techniques, you can come up with all sort of creative applications of stacked symbols and rotation.