I don't have specific recommendations for a mechanical RGB keyboard around $50, but I would strongly recommend choosing a brand other than Rosewill, for any parts that matter, even if you have to wait and spend more later for a quality keyboard.
I have a glitchy Rosewill mechanical keyboard and a 950W Rosewill PSU which barfed all over itself under much less than 950W load.
Mine is a few years older, not RGB, and it's possible that their quality control has improved but I wouldn't count on it. The glitches I've experienced are:
1. micro USB connector to keyboard isn't as secure as it should be
2. in Ubuntu, had to press quotes twice to register once. This is obviously minor and was not reproducible in Debian, so I'm using this keyboard right now, but that only makes it adequate, not something I can recommend.
IMO, Rosewill is a cheap knock-off brand, not the lower-price-for-similar-quality brand that I hoped when I purchased the above. I can only recommend that brand for inconsequential gadgets like
http://www.newegg.com/Product/Product.aspx?Item=N82E16899261023
http://www.newegg.com/Product/Product.aspx?Item=N82E16803009317
and simplistic parts like
http://www.newegg.com/Product/Product.aspx?Item=N82E16817997010
http://www.newegg.com/Product/Product.aspx?Item=N82E16812119582
...and only if they're on sale, significantly below the price for the equivalent part from a reputable brand.