Rocket Internet, if I understand correctly, work by bringing business models invented by american startups to overseas markets, and they're good at it (which means they offer good products and services, not crap).
So as an Israeli, I really appreciate what they do. For instance, we don't have Zappos service in Israel. Shoe shopping sucks, so I wish Rocket Internet would come and build a Zappos in Israel.
If I were busy dominating the american market and I'd suspect RI want to clone me abroad, I'd do two things:
1) Sell to them, because I know if they care enough there's no way I can avoid my product falling into their hands.
2) Contact the Samwer Brothers, inquire if they're interested in my niche and mention the idea that they start a company to resell me overseas, which would be much cheaper than developing a clone and competing with my eventual overseas expansion.
Sidenote: I heard they treat their employees badly. That's irrelevant to this post, and thus to my answer.