Statics 5.22 - The intensity of the distributed load is 3kN/m determine the reactions at the roller. 

Hey thank you, I am happy to help!

Thanks!

Hello my friend, Lets start with the force at roller A. Rollers only apply a force normal to the surface they are touching. In this case its at an angle. Second, at B we have a pin; therefore pins only apply a vertical and a horizontal force to our system at that point. (I believe you confused a pin with a fixed support, fixed supports do create a moment reaction.) Finally, the summatory of moments at point B is equal to zero because the overall system is not moving. Since we are in statics it is safe to assume every summatory of forces or moments should be equal to zero, again only because the system or object is not moving. In your next semester you will probably have Dynamics which is when the objects are now moving and the summatory of forces and moments are now NOT equal to zero. I hope this helps!

@LearningbyTeaching thank you, sir, for the quick response. I appreciate it