Rocket German is my 3rd Rocket language course: it is awesome and it let me learn the basics quickly.
I would highly recommend it to get a primer of the language and as a support to grammar classes or books.
If you need a basic to intermediate command of the language, Rocket is definitely enough, plus it helps really A LOT with pronunciation!
Then, if you are aiming to master a foreign language I can share what worked for me. I learnt French and Portuguese in less than 1 year (well enough to be able to work in those languages) and I am progressing very quickly with German right now.
I have started with Rocket premium level 1, then I have taken few private classes while continuing with Rocket.
At the same time, I try to listen to the Radio and watch movies in foreign language whenever possible.
Whatever is your goal, I cannot stress enough the importance of Rocket Language in learning a new language.