Playing any class at more than just a basic level requires keeping track of timers, procs, charges, and more. It is next to impossible to do this without help and there are several addons that are designed to do this for you. One of the most popular is WeakAuras.
WeakAuras is highly customizable and quite complex but once you have installed the base addon, if you aren’t up to creating your own UI, you can import a WA set created by someone else. Because everyone has different preferences, you may have to try out more than one to figure out what works best for you. Below are links to WAs created by rogues for rogues.
Gray_hound’s WA is an all inclusive package that serves all three specs and switches automatically when you change spec.
Notter’s collection is Assassination oriented but includes both other specs as well.
If you enjoy Infexious Gaming’s videos, you may want to check out his WAs.
Potato has set for each spec.
Mystler also has a nice selection.
If you want to search for more options or specific WAs, Wago.io is a searchable database collection designed specifically for sharing WAs and other similar addon elements.