Does this mean that the shape of the slots in the docking cone interfacing with the ball on the probe lead to roll alignment?
Yes. Bar minor changes, this aspect of the docking design has remained unchanged since it was first implemented in the 1960s.
As Organic Marble says in his comments (i cannot see the PDF):
It calls the slots "trapezoidal" - I'd interpret it as saying that the latches on the tip of the probe go into the slots, which narrow down and constrain the vehicle in roll.
Correct, you can see the trapezoidal slot - outlined in green - below:
when the probe head enters the drogue, the (4) latches extend from the head and engage within the (4) sockets at the end. When the probe head retracts (screws), the latches are dragged along the edge of the narrowing socket edge until they become fully engaged and cannot move from this position (to do so, the latches would be retracted, for removal of the hatch and for undocking). This is where the final, minute (within 10 degrees of error), roll alignment is carried out.
Small video to show its operation:
latches on the probe head seem part-extended in this view, alignment levers (with wheels attached) can be seen retracted inbetween the 'cone legs'.
Larger video culled from ESA that shows the graphical representation of the docking procedure, with the probe head contacting the drogue cone, entering the socket when the latches catch and then the probe head retracts, simultaneously the alignment levers have extended forward into the drogue to alleviate friction as final pitch and yaw alignment is carried out, and as the latches on the head are dragged along the edge of their socket the final roll alignment is performed, bringing the alignment pins and sockets and interfaces into alignment on the docking rings, and final retraction beings the hooks of the 8 (or 12 on APAS type) latches together for hard-docking sealing.
trapezoidal sockets, allow for a very mechanical way of roll alignment.
From OP's PDF link:
When the probe head has been caught by the drogue socket and relative spacecraft motions have
been attenuated, the docking mechanism’s drive is actuated to pull and align the spacecraft. The
alinement is accomplished by the narrowing socket slots and through expanding the linkage assembly (for pitch and yaw alignment) by a cam rotating synchronously with the screw movement.
Early development sketch, showing socket design:
Text, from left to right: Docking mechanism, Receiving cone socket, Profiled groove
на пассивном — приемный конус с ответным гнездом под головку штыря. Профилированием паза обеспечивают выравнивание по крену в процессе стягивания.
On the passive - a receiving cone with a counter socket under the pin head. By profiling the groove, roll alignment is ensured during the tightening process.