I don't think there is a native equivalent of rotx() that uses radian as input. You can convert radians to degrees using the rad2deg function. You could write your own rotx_rad() function that incorporates that automatically.
function R = rotx_rad(theta_rad)
% Rotation matrix about the x-axis (input in radians)
% R = rotx_rad(theta_rad) returns the 3×3 rotation matrix for a rotation
% of theta_rad radians about the x-axis.
% Convert radians to degrees and call rotx()
R = rotx(rad2deg(theta_rad));
end
