RoTLD is the main registry for .ro domains and all management operations of this kind of domains can be made from the their panel. You can modify the nameservers for .ro domains by following the folowing steps:
1. Go to: www.rotld.ro
2. From the upper side select .ro Domains » On-Line Administration
3. In the new opened page you will need to authentificate with your domain credentials, like in the image below. After, click Next.
4. In the next step, we will choose from domain configuration options the one we are interested in, namely Nameservers
5. In the new page that opens we will enter the desired nameservers, as in the picture. To go on click on Update.
6. An email with the confirmation key for the changes will be sent to the owner's email address:
7. Check your email address and click the Confirm operation button in your inbox. Make sure you are logged in to ROTLD before opening the email link.
If everything went well, you will receive a message like:
"Updating was successful. Please check the updated information!".
!!!Please note that the DNS propagation of new nameserver can take up to 24 hours.!!!