“Excited” by the signing, Martin told Rangers’ website: “He is a player who we thoroughly enjoyed working with during my time at Southampton.
“His leadership, professionalism and quality were a huge asset. He is joining on the back of two promotions so helps bring a real winning mentality to the group.”
Fernandez arrives from a side who they finished 18th in League One, but Martin views him as having “a huge amount of potential”.
“He has a strong physical presence, is a commanding defender and I believe in this environment we can help him develop and provide him with the opportunities to take his game to the next level,” he said.
Rothwell came through Manchester United’s youth ranks and, after loan spells with Blackpool and Barnsley, joined Oxford United.
He moved on to Blackburn Rovers and then, in 2022, to Bournemouth and has made 351 club appearances overall in his career, scoring 24 goals.
A “delighted” Rothwell says there were two main factors that persuaded him to end his three-year spell with his Premier League parent club.
“The size of the club speaks for itself and, as soon as the interest was there, it was an immediate yes from me,” he said.
“With Russell coming in too, it made that decision a little bit easier because working with him in the past and I know what type of guy he is and how he wants to do things. That was an even bigger pull for me.”
Rothwell follows right-back Max Aarons to Ibrox from Bournemouth, the 25-year-old having joined on a season-long loan, while 22-year-old fellow midfielder Lyall Cameron was a free agent arrival from Dundee.
Meanwhile, Fernandez, who made 42 appearances last season, admitted he “was shocked” to have received interest from “such a big club” as “I haven’t played at this level”.
“But it is something I want to be part of – I think I can kickstart my career and have a good journey here,” he said as he arrived for an undisclosed fee.
Martin’s side open their season at home to Panathanaikos in the Champions League second qualifying round first leg on 22 July.