Rhodes was presented with Rovers' player of the season award before kick-off and scored his 27th goal since joining from Huddersfield in August.
Barnsley and Rhodes' former club are two of the four teams that lie between Blackburn and the drop zone and the fact that the Yorkshire rivals meet each other to round off their seasons means Ewood Park caretaker boss Gary Bowyer can breathe easily.
Palace led through Scott Dobbie but Ian Holloway's men will look uncomfortably over their shoulders from fifth position next weekend, with Bolton, Nottingham Forest and Leicester all within touching distance.
Timely breathing space might have been earned during the second period when Glenn Murray and Mile Jedinak his the crossbar for the visitors.
Bowyer was forced into three changes after David Dunn, Colin Kazim-Richards and Marcus Olsson picked up injuries in midweek. David Goodwillie, Nuno Gomes and Josh King came into an attacking Rovers line-up.
Jedinak replaced Alex Marrow in Crystal Palace's only change and top scorer Murray passed up a half chance from an early corner.
Opportunities were few and far between until midway through the half when Blackburn established themselves as an attacking threat - King's cutback narrowly evaded Nuno Gomes after a driving run and, moments later, Rhodes fired over on the turn.
Back came Palace and Blackburn defended a flurry of corners successfully only to see their good work undone in the 28th minute.
Dobbie collected Aaron Wilbraham's flick-on and got the better of Grant Hanley to produce a smart finish.
The former Swansea forward almost doubled his tally six minutes later, watching a free-kick fly past the post from 25 yards with Rovers goalkeeper Grzegorz Sandomierski at full stretch.
Damien Delaney then passed up a chance as Hanley failed to clear another set-piece and the Eagles defender would soon rue his profligacy.
King released Rhodes following a fine pass from Josh Morris and the Scotland international burst clear to deftly lift the ball over Julian Speroni and home from an acute angle.
Five minutes into the second half Morris was involved once more, twisting and turning before going down under a challenge from Kagisho Dikgacoi. Referee Phil Gibbs was unmoved.
The young full-back could not stay out of the action and soon afterwards Rhodes and Goodwillie came close from his dangerous ball into the box.
It was a thrilling end-to-end period and, in the 52nd minute, Murray rattled the crossbar after a long ball undid the Rovers defence.
With an hour played, Palace again tested Sandomierski's furniture - Jedinak clipping the top of the bar from Dobbie's corner.
Morten Gamst Pedersen, on at the break for Nuno Gomes, and Murray blasted wide for their respective sides before the latter unsuccessfully pleaded for a penalty having come out second best in a penalty box tussle.
Rhodes was alert when Palace coughed up possession with a quarter of an hour remaining but strike partner Goodwillie thrashed over left footed when played in.
The final chance fell to Delaney who headed wastefully wide from close range after Dikgacoi picked him out.
- Sports & Recreation
- Glenn Murray
- Nuno Gomes
- Mile Jedinak
- David Goodwillie
- Gary Bowyer