Rholang is pretty different from all other programming languages, so there is not really another one which we could expect people to know first. An understanding of the computational calculus the language is based on would be helpful (open access paper on it available here), but we understand that not everyone has a background in theoretical computer science, so this is not required.
We're still working on creating good introductory materials for learning Rholang, but you can take a look at the tutorial and just try playing with it yourself. Also feel free to ask any questions you have along the way.
As Michael stated, we are working on blog content to help new and experienced devs understand its history and what it is. The blog posts should be coming out within the next week(going through edits now). Stay posted, and I will send you a link to the blog once it finished.