Rogaine definitely helps, but not as much as Finasteride. My doctor (Dr. Bernstein from Bernstein Medical) told me that Rogaine is responsible for 20% of treatment, and Finasteride is 80%.
I don't know why he told you this because hair loss treatments really don't work like that. It's not a fixed percentage of help for each one and Minoxidil and Finasteride certainly doesn't help treat everyone. Minoxidil is a growth stimulant that in about 1/2-2/3rds of people gives some degree of regrowth. Finasteride addresses the route cause of hair loss by inhibiting DHT, the hormone which directly/indirectly causes hair to miniaturize and eventually stop growing completely. If you are on just minoxidil the chances are you will not be maintaining your hair.
Hajo1992, assuming you are, like most of this forum, balding under 30 then the balding is almost certainly too aggressive to be stopped with just minoxidil alone. You will probably need an AA, be it Finasteride, Dutasteride or RU. If you have had sides in the past with finasteride then it might be worth trying RU which is a topical solution that inhibits DHT in the scalp. It can however, go systemic just like Finasteride. Unfortunately these are the only options really available to you for the moment. There are some very exciting treatments in the pipeline, If you want to see some of them user Hellouser recently went to the 2015 World Hair Congress and has posted a lot of threads under that section. You can find it from the Forum page.
As for if Rogaine is working for you, it is difficult to say, by the 4 month mark most people have at least seen a sign of regrowth, Minoxidil has been known to cause hair loss without the hair ever growing back while on the treatment. This is what happened to me, I took Kirkland Minoxidil for nearly 3 months before I got fed up of the state it had left my hair in, I had 0 signs of regrowth from it and lost a lot of density across my whole scalp in that time. Also near the end I realized minoxidil really isn't something I want to be on for the rest of my life, I didn't fancy applying it everyday and it can age skin horribly. It's up to you if you want to continue treatment of it, I think the general consensus is you should try it for 6 months before deciding whether to stop or not.
Can I ask why you got 2 Hair Transplants without being on an Anti Androgen? What surgeon did you go with? I would have thought they would at least advise you to be on an AA at the least. And maybe even have turned you away if you weren't on one.