Bolton born Ashworth,, who started out at Wigan, hopes to be a big success and earn a longer deal and speaking to the Star, told of his unfortunate spell down South.
"I know Ian was a big fans favourite here but I'm confident that if I get my chance to start that I will prove myself and stay in the team," he said. "The manager has said that he wants a lot of competition for places here so it up to me to impress him and get a place in the starting line-up.
"It was unfortunate at Orient because the manager's changed three times while I was there," said Ashworth, who will be suspended for the League Two opening day clash with Lincoln after a red card. "Martin Ling got sacked only two weeks after he signed me.
"I thought I did well in the games I played last year but the boss Russell Slade wanted to go for more experienced players. I never felt that I was given a fair crack at Orient. I knew I needed a new challenge and I'm absolutely delighted to sign for Rotherham.
"It wasn't that long ago the club was in the Championship and I thought that this would be a good opportunity in my career.
"It is great to be back in the north and my aim now is to impress the manager and hopefully break into the team."
He added: "I watched the play-off final last year and thought they were unlucky. They should have gone straight up but they had a dip in the middle of the season. If we can get on a winning run, I don't see any reason why we can't be competing for a top-three spot."