Yes, you can do this by modifying the 'Rotation' property of the text object's handle.
Please take a look at the following MATLAB code for an illustrative example:
x = 0:pi/20:2*pi;
y = sin(x);
plot(x,y);
% create some text objects on the plot and get there 'handles'
t = text(pi,0,'\leftarrow sin(\pi)');
t1 = text(1,0,'text1');
t2 = text(2,0,'text2');
t3 = text(5,0,'text3');
% Specify rotation angles for the 'text' object handles
t.Rotation = 90;
t1.Rotation = 30;
t2.Rotation = 180;
t3.Rotation = 45;
