If you wanna use rockets effectively you need damn good intelligence (potential targets) and the ability to hit them (accuracy). And there is evidence the Russians are lacking both to a certain degree.
When you imagine two rocket systems that are pointed at each other there are multiple factors deciding which side wins. Accuracy and range being two of them.
The western HIMARS rocket system used by the Ukrainians is far more accurate than everything Russia has (in sufficient numbers) and the range is (afaik) better than the artillery range of the russian side. Which means the Ukraine can hit them, before they can hit the highly mobile HIMARS (which might already be at a different place once they fired their payload).
That being said one of the major factors in this war has always been that one side is defending. That means Ukrainians have better morale and better intelligence, because the people living in these regions might still supply them with information about Russian troups.