"ro'n i'n"

Translation: I was

[StephenDunscombe]

Is this a contraction of "Roeddwn i'n"?

[ibisc]

Yes. And without something following the 'n it is not really translatable - it is a sentence fragment which needs completion. For 'I was', or 'I used to be', just roeddwn i or ro'n i would be correct.