He scored nine tries during 30 appearances for the Robins on his season-long loan from Huddersfield Giants, but a permanent deal never materialised and he instead rejoined League Leaders Shield winners Castleford.
The sides meet tonight in a rearranged Super League game after the original March match was postponed due to snow.
Recalling his time with Rovers, Ellis said: “It was good. Obviously I didn’t want to drop down a league, but they are a quality club.
“The fans are great there and it is a very hostile place to go. I did love it there and it was nice to play regular every week and be –not top dog as that’s not the right word – but a main player.
“It was good for my confidence. I made a lot of friends for life and wouldn’t change it for the world.
“I’ve got a WhatsApp group with people like Danny Addy, Robbie Mulhern, Nick Scruton, Chris Clarkson and Thomas Minns.
“We’re all really close and there’s other players I still keep in touch with. I do miss them a bit.”
Admittedly, Ellis did join Grand Finalists Castleford, whom he originally played with in 2012-14, but they have struggled to recreate last season’s stellar form.
They were embarrassed at the hands of leaders St Helens last week – Ellis’s first professional club – and are fifth in the table.
Rovers are 11th, desperately hoping to escape the Qualifiers and aided by a stunning win against Wigan last time out.
Ellis, 28, admitted: “We’ve had a tough week. We’re disappointed with what we dished up last Thursday night. Now we’re in for a tough game at KR. They’re in the bottom four, but are playing pretty well. We have to be on it.”
Castleford have moved to ease their full-back problem by signing prolific former Sheffield Eagles No 1 Quentin Laulu-Togage’e from Halifax until the end of the season.
The ex-Samoa star, 33, left Sheffield for Toronto Wolfpack in 2017, but departed in April after they bought Gareth O’Brien.
He now finally – and unexpectedly – gets a chance to make his mark in Super League.