I'm guessing you're asking how to re-invest with the ETH that gets mined and added to your personal wallet? Whenever ROCK2 is available on an exchange, you can potentially buy it with ETH, but since there is no more available in the ICO, you would need to wait until someone is selling theirs. Not exactly sure how that works (it depends on the exchange) but you would probably submit a buy order for a certain price, then it would buy automatically when some ROCK2 comes up for sale.