Roobarb is a pretty enjoyable cartoon and a hidden gem. I wish this show had at least a few more seasons because it's sad how this show only got one with 30 episodes (though it did get a really good reboot).
The art style is very unique, rather than having the generic way shows are animated, Roobarb is completely animated with marker pens with plain white backgrounds, which is impressive to say the least.
The plots and characters also have their own charm, especially our protagonist, Roobarb, who invents stuff that goes wrong in many hilarious ways. Grange's writing is great, with many interesting storylines that are short and simple, but entertaining as well.
Richard Briers is a great voice actor and narrator, seeing a lot of old UK cartoons only have one actor for all of the roles is very fresh and talented, and Briers is no exception. Shame he died in 2013 though.
The music itself (especially the theme song) is really catchy and upbeat, much better than the bland and generic music from the disaster known as Peppa Pig.
The only thing about this show that does not hold up is the animation. Even if the show does have a unique look, the animation (even for the time) is awful. It can look passable at times, but most of the time, it's very rough and sloppy. The character designs, while good on their own, can look inconsistent between episodes or even separate scenes and the lack of lip-synching for most episodes makes the cheap animation more obvious (it's made even worse by the fact that there are scenes/episodes that do have the mouths move when characters talk).
Now, I have nothing against the late Bob Godfrey or anyone working on the show, nor do I blame or intend to disrespect them for this. Godfrey had done other animations, and they actually do look decent with the limited style (Noah and Nelly another Godfrey show made two years later, and from the clips I've seen (not seen the full show, this is just for research) the animation, whilst still being limited and having some of the traits Roobarb had in it's animation such as the lack of mouth movements, looks alright for a 70's TV show. I think Roobarb's animation moreso suffered from a bunch of different animators alongside Godfrey working on the same episode, and some of the same or completely different ones working on others. Not blaming them either, but I feel that there was (and this is just a theory, don't take this as factual) a lack of communication to keep everything consistent-looking. I think that if there was a more consistent look, less sloppy movement, mouth movement, and overall more communication (presumably, I'm just making my own conclusions), then the animation would have turned out better. Funnily enough, despite being flash-animated, the reboot's animation is what I'd imagine the original being like if that were the case (barring the lack of mouth movements).
But despite the really rough animation, this show is still great, and I hope another reboot gets made soon since the older reboot (Roobarb & Custard Too) also only ran for one season (such a shame as both series had potential to become a full series with more seasons). Roobarb is a classic and I highly recommend it.