If I got you right (if you need model to chase an other model and turn on its roll), then you are doing wrong...
Here is what I can offer:
action follower()
{
VECTOR temp;
while(1)
{
vec_set(temp.x,player.x); // turn to player
vec_sub(temp.x,my.x);
vec_to_angle(my.pan,temp);
my.roll += 10 * time_step; // play with 10
wait(1);
}
}
This will turn model to player and will turn its ROLL as well.
All you need now, is adapt this to your needs (ENTITY* pChassis etc) and move it with C_MOVE instruction.
If you'll need help PM me. Enjoy.