If the Rosa didn't work for you, don't worry. It's not you and it's not the toy. Sometimes things don't just work the same for everybody. I'm kind of in your situation but with a different product - the Bathmate pumps.
I've been trying it regularly for at least 3 months, and I have to say, i've not seen any of the results almost every other glowing review has said you will see. I spent ages thinking "Oh I must be doing something wrong" or "I'm clearly broken" - but I'm not doing anything wrong, and I know I am definitely not broken - it's just a product that clearly isn't going to work for me.
You have to remember that everyone is different when it comes to their preferences and likes, and everyones anatomy reacts differently to stimuli - and just because a toy gave one person mind blowing orgasms, it doesn't mean it's going to give it to someone else.
The other thing to consider is that when you read about a toy that's supposed to be amazing, your expectations are already way up, so when it doesn't blow your mind straight away, immediately it puts a 'block' on you and it can be difficult to get yourself into the mindset of actually enjoying the toy because it didn't do what you thought it would right away.
The best thing to do would be to just take it slow, don't expect too much from it, just experiment with the different settings, and get a rhythm that works for you. Take your time - and hey, if it still does nothing for you, then don't worry about it. It's time to send it back - at least you tried it and gave it a shot. It's just not for you.
Don't put so much pressure on yourself/on the toy and you would be surprised at what you can achieve.