Blackburn continued their climb up the table as they stretched their winning run to three games.
Keswick started the day higher but thanks to a 100 per cent kicking record from Leon Fifield, Blackburn managed to leapfrog their opponents in to fifth place.
Blackburn applied the pressure from the off and they were rewarded with a fourth minute try when the ball was spun through hands for Greg Jansen to score near the posts.
Fifield slotted over the first of his four kicks to make it 7-0.
That lead was cut to two points as Keswick scored a try of their own. But the home side quickly set about re-establishing themselves and crossed for a second try Richard Maudsley took the ball at pace to score. Fifield again was successful with the kick.
Fifield slotted over two penalties after the break to stretch the lead to 20-5 before Keswick replied with a try and a penalty to earn a bonus point.