Thank you for reaching out to us and Welcome to Wefugees!
As you've already outlined- if Romania issued you a visa, they are technically responsible for your asylum case according to Dublin-III Regulations. That means, once you enter Norway and claim asylum, they may send you back.
However, this website "welcome 2 europe" states that there have only been individual cases so far where refugees were transferred back to Romania: http://w2eu.info/romania.en.html
I cannot advise you to be in any country illegally. You can find a good explanation of dealing with Dublin regulations on the following thread from our platform: How to avoid the Dublin regulation by waiting for 18 months?
And this one: Dublin regulation - when does the 6 months deportation limit start?
I'm not a lawyer, but as I understand it, your asylum case in Norway may be negatively impacted by your hiding/ Dublin may still apply to you because you never left the EU. If you leave the EU for more than three months and return to Norway, you can apply for asylum and it can be considered a separate case (unaffected by Romania issuing you a visa before). Find more info here: Is it possible to avoid the Dublin III regulation by leaving the EU for more than 3 months?
I hope the sources and threads I shared with you here are helpful. Feel free to reach out to us again if you need any further assistance!
All the best,