Prop forward Walker joins for a one-month period, while centre or winger Uaisele is back with the Rams for a second spell following a short stay with the club in 2015.
Walker is already a veteran of more than 50 Super League appearances and has spent the vast majority of his playing career in a full-time environment.
“We have five front rowers out injured and ten of our squad are sidelined in total, and Jonny brings with him some experience in the forward position that we need,” Rams head coach Glenn Morrison said.
“While Etu is somebody we tried to get on loan a couple of weeks ago. He’s been here before and he’s a top performer. He’s a great person off the field too, and really good with the youngsters.
“Both players are here to get some game time and to enjoy their rugby. We don’t have much cover with the injuries we have and both players will bring a lot to our team.”