The 37-year-old signed a new one-year deal last week after previously looking set to leave the club - but the deal sees him take home less money each week.
He said: "The deal was not what I wanted, it's a lot less than I was on (last season) but if I turned it down then I could have gone two or three weeks without a club - or not even got one at all.
"I took the time to think about it and then I phoned up last Saturday and said that I wanted to sign the deal at training this week."
And Royce admits the lure of League One football was a major part in his decision to stay with the Gills.
"We got relegated two seasons ago so there's a score to settle - I want another crack at League One," he added. "Last season we got promoted and won at Wembley, and that really whetted my appetite again."