Republic boss Mick McCarthy was at the Keepmoat to see the forward's goalscoring turn in the win over Peterborough United a fortnight ago.
It raised hopes of a call for Sadlier, particularly after he was named in a provisional squad for the last round of international fixtures.
But he insisted, regardless of whether he received a call-up, that his primary focus would be Rovers.
“Being in the provisional squad a few weeks ago for the last two games, I obviously knew that I was in and around it,’’ he said.
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“That was the first step forward of trying to get into the international set up again.
“It was good to know that he was there and that I’m in contention to get called up.
“I’m just focusing on my club and I know if I play well the international thing will happen eventually.
“Whether that's now or not, I’m a step closer and I'm just going to keep working hard.’’
Having the manager of the national team in the stands could easily have proven a distraction for some players.
But Sadlier was determined to take McCarthy’s presence in his stride – which he did with a superb solo goal to double Rovers’ lead.
He said: “Ten minutes before the game I knew. My dad was in the crowd so he told me.
“It didn't affect me. If he’s there or not, it’s the same really.
“It's just another person in the crowd really.
“It's very nice and it gives you a little boost knowing that he's there watching you.
“It wasn’t a bad game to come to.”
Sadlier remains determined to force his way into McCarthy's thoughts in the future as he targets a first senior cap for his country.
“I think it’d be the proudest moment of my career to date,’’ he said.
“I think it’s the pinnacle for any footballer - wanting to represent their country.
“I've come through from the U15 right to the U21s with Republic of Ireland, plus I lived there for three years so I know what it means to play for the country.
“I've got friends in the squad as well.
“It'd be amazing and would be a proud day for me and my family.’’