It can be done DIY. Before you try anything you have to make sure the mast (part bolted to the roof) is leveled in all directions (pointing straight up). If it's not, then you're shooting in the dark. If you had signal before then you should not have to readjust the skew and elevation on the dish unless the roofers rough handled it. Check and start with the recommended settings that show up on the receiver's setup screen. Point the dish in the direction it was before they took it down--starting further to the left than you remember it to be.. Then, turn it VERY SLIGHTLY to the right. Wait a few seconds. Listen to the tone signal coming from the receiver--if it's too far to hear then call somebody on cell phone so you can listen that way and/or have them tell you the signal strength. Turn slightly to the right, wait a few seconds, listen to tone. Turn slightly to the right, wait a few seconds, listen to tone. The key is SLIGHTLY because too much and you can overshoot. Keep repeating that until you hear the tone from the receiver indicate that it's picking up something. When you have a signal lock you can wiggle left and right until it peaks. You can also adjust elevation (up/down) if you're OCD. Everything I have ever read says set the skew and leave it.
If you're a DIYer you can do it. Plus you get the satisfaction of knowing you DIYd it.
I've setup/alligned dishes before and it takes a little bit of patience but you don't need anything super fancy beyond what you have. If you had satellite internet where you're trying to beam something OUT then yeah that's when you call in the pros with the expensive equipment.