Origin

Star Trek Canon Special Note
Not everything listed in the origin is Canon.  That is because only television shows and movies are considered canon for Star Trek.  This being a comic website there are many things here that are not canon.  So unless it is contradicted in film it should be listed as part of the character biography.   
 
Rom is the brother of Quark and the father of Nog (the first Ferengi in Starfleet.)  Rom himself was the first Ferengi in the Bajoran Militia.  Rom never had "the lobes" for business.  As such he followed his brother in finance.  So when Quark opened a bar on the space station later known as Deep Space Nine, Rom followed.  
 
The station was in orbit around  Cardassian occupied Bajor.  So, Quarks bar was run under Cardassian law.  That is until the Cardassian and Federation treaty that changed the boundaries and put Bajor into Federation Space.  On he way out the Cardassians gutted the station and destroyed all the businesses on the promenade including the Quark's bar.  This combined with the uncertainty of the new Bajoran provisional government lead Quark and Rom to abandon the bar and leave. 
 
At the same time the Benjamin Sisko arrives as the Federation Commander of the station and Rom's son Nog gets arrested for breaking and entering.  Sisko wanted Quark to keep his bar open to inspire others to stay and used Nog as blackmail to get him to stay.  Quark agreed and so the whole family stayed on the station.

Creation

The character of Rom was created for the television show Star Trek: Deep Space Nine.  The actor that was cast as Rom Max Grodénchik had originally tried out for the role of Quark but stayed on as an extra who later turned out to be Rom.

Character Evolution

Rom stayed on the station and was blamed for everything Quark needed him blamed for he had a reputation of being an idiot.  Even Odo said he couldn't fix a bent straw.  The fact of the matter was Rom was quite an engineer but because there was little value in it he hid in his brother's shadow and tinkered around the bar fixing the replicators when they broke.  His skills were missed by almost everyone.
 
His son Nog noticed and was proud and still somewhat ashamed of him.  Nog knew he was a genius but would never get his due.  He also knew that he didn't want that life and he wanted to do something more meaningful and so he joined Starfleet to have a better life.  In a way Rom was inspired by his son and joined the Bajoran Militia.
 
A Bajoran dabo girl named Leeta also noticed Rom and fell in love with him.  They had a sweet relationship and were married after a couple years.  This was the big turn around in Rom's life.  After the three events of his son joining Starfleet, he joining the militia and his marring the beautiful Leeta people began to look at Rom differently.  After seven years of living on Deep Space Nine Rom became the Grand Nagus of his people.