Sitting for CAT again is honestly not a very easy decision. So I will suggest you go for IIM Rohtak itself. This decision will be beneficial under the following circumstances 

• If your past academic performance is not really good. This is because the older IIMs lay emphasis on past academics too much which in reality cannot be changed. So why risk a year when the chances are nearly zero?
• If you already have 2 or more years of experience, it’s better you don’t forgo the opportunity.
• If you are interested in domains like Finance or Marketing, it’s better to join now. This is because working too much in the IT field limits your chances of getting into Finance and Marketing.

So based on these points you can come up with a decision that’s best for you. Just remember that despite being new, IIM Rohtak belongs to the IIM family which in itself is a brand.