I'm really not into it for the reasons stated above. How familiar are you with the products in Komplete? Stuff like Absynth, Massive and Reaktor will cover way more ground in terms of sound design possibility. Shitloads of presets out there too. With the Roland cloud you get straight up classic Roland sounds and the System 1/8 Vsts, which don't really add a heap to the stuff you have unless you want that gooey analog thing that the Juno/Jupiter emulations go for. And even then I'd rather buy one really good dedicated virtual analogue synth like Steinberg's Retrologue or Uhe's Diva than subscribe to a service like Roland cloud.
Serum is great, I had it for a few months before stopping my subscription as it didn't suit my workflow but it's legendary for a reason. Super flexible, massive scope for sound design and a million presets available.
I'm having a shitload of fun with this guys synths at the moment,
https://www.fullbucket.de/music/fb3300.html especially the PS3300 clone, which is a basically unobtainable Korg 48 voice polyphonic synth from the late 70s. All Free.
But yeah dude i think there are a million better options out there