How does stall risk in paramotors differ from that of conventional fixed-wing aircraft?
I suppose with paramotor you mean a powered paraglider, as pictured below.



Paramotor (picture source)

Since they obey the same laws of physics, they also stall, just like a fixed-wing aircraft does. There are, however, some peculiarities which should be mentioned:


The shape of the wing is produced by ram air filling the parafoil, so speed will help to keep the wing inflated and in shape. At low speed and in gusty winds the risk of the parafoil collapsing (severe deflation) is higher. This was the reason for several fatal accidents in the early times of paragliders, when the aspect ratio of high-performance parafoils was increased beyond safe limits. Today's designs will normally quickly recover from a deflation event, but not without a substantial loss of altitude.
The pressure forces on the parafoil will change its shape depending on its angle of attack. At low speed the angle of attack is higher, resulting in a suction peak close to the leading edge which in turn will increase the local camber of the foil. This leads to severe lift loss in a stall, and recovery needs some altitude. A fixed-wing aircraft, on the other hand, can employ an airfoil with only little lift loss in a stall, so recovery needs less altitude. This is by no means universal - there are also fixed-wing aircraft with less benign stall characteristics.
If the stall on a fixed wing starts near the wing tip, the aircraft might enter an uncontrollable roll. This can happen in steep turns and with badly designed aircraft. This is not possible in a parafoil; it might instead slide sideways with a partially collapsed parafoil, but stay upright due to its low center of gravity. If the pilot panics and pulls his brake lines on one side during a stall, the parafoil can enter a spin. Similarly, if the pilot of a fixed-wing aircraft insists on applying rudder when stalled, the aircraft can also enter a spin.


Generally, due to their low wing loading and the drag of the raiser lines, paramotors fly at much lower speeds than aircraft, so accidents involve less energy, but the pilot has no protection around her/him, so fatal accidents do occur more regularly than with fixed-wing aircraft. For paragliders, Wikipedia gives a number of 2 fatalities per year for 10.000 pilots.