Hi Lucy,
If you check the 1901 census online you will see two Isaac Rodgers aged 20. (
www.nationalarchives.ie)
Both lived in/near Lurgan ie. John Street and the townland of Ballygargan(approx halfway between Lurgan and Portadown. Maybe these two were the same person as one is listed as a boarder and I have been told by a member of the Proni staff that sometimes this was written instead of visitor, depending on who was recording the info. Their jobs are very similar which made me think they may be the same person, however many people had the same job /name so possibly not. Just a thought!! Having said that only one of the isaac's listed can speak Irish.
The Isaac listed in Ballygargan can speak both irish and English. I do not think it uncommon for a person living in that era to speak both language irrespective of what denomination they were. When I first read your post in May I discussed it with my Dad(who is 81 ) and he recalls people from the protestant persuasion from his generation who could speak in it. I would expect the Ballygargan Isaac to be yours as it is counted as Portadown rather than Lurgan and you stated that he was born in Portadown.
Also while browsing through the 1901 census for my own family from a neighbouring townland to Ballygargan I found that both my Great Grandparents also spoke Irish.
You also ask could they be immigrants... I suppose we all were at one time but the Ballygargan Rodgers/Rogers had lived in the area for quite a while and today there are still Rodgers living in the area . As with most rural townlands many of the families married into each other on more than one occasion. My own family has connection(although distant only via marriage) with the Ballygargan Rodgers.
It also states on the census form that if the person speaks both languages it is to be recorded as 'Irish and English'. It does not mention recording it as their first language witten down first.
Hope this helps a bit but maybe someone with more knowledge of the subject can help.
If you want a contact for the Rodgers family let me know . I do know that several local twigs of their tree are into their family History plus a direct link also. How are you connected to them?? Hope you can understand this and sorry for being long winded!!:)
Regards,
Aljepeka