If you are a small team getting ready to bout, you are probably worried about the audio and video requirements. LADD worried about this too. Here's what we currently use:
There are good reasons to hire a DJ: it's one less thing to worry about, and you don't need to drop a lot of money on a sound system. But after a few bouts you might realize you can save money by doing it yourself.
The important thing about sound at a bout is the announcer, not the music. I think a small team would do just fine with a single powered speaker, two wired mics (reasonable wireless mics are super expensive, and your announcer shouldn't be wandering around), and somebody's MP3 playlist. The Harbinger APS-15 provides a built-in amp and mixer, so you really only need these two items.
You do not really need to hire a DJ if you can provide a powered speaker and mics. I have been to a number of bouts, each time with a keen ear on the music. I've talked to as many DJs as I could, and with the notable exception of the 2011 Nationals in Denver, they have all told me their job was to set up equipment and play a mix CD provided by the team, or a playlist on some team member's MP3 player. They've all been sort of bored.
You should also strongly consider not playing music at all. Most music requires royalties payments, and playing without securing the right licenses can incur legal threats and other BS you don't want to waste time. Lastly, can you name another sport that has music during gameplay? Just skip it.
If you do want to go for a full mobile DJ setup, though, I have a separate DJ article you might enjoy. Total cost is $650 for that.
Your scoreboard should show period time and jam time. Because most hockey/basketball/etc. scoreboards only have one timer, most teams use a projector and computer. The Los Alamos Derby Dames has a free roller derby scoreboard you may use, and there are a few other free options available.
When shopping for a projector, it's easy to get overwhelmed by the options. Look for high lumens and low resolution.
Lumens are the units that measure how bright a projector is. Unless you are playing in a dark room, you will need at least 2500 lumens.
You need to test some projectors in your venue before committing to a purchase. The deciding factor here is "ambient light": how much light is already in the area for your projector to compete with. This is really the only way to know for sure what your needs are.
The Derby Dames bought a 2800-lumen projector, after trying a few out in our outdoor (shady) venue. 4000 lumens or more would have been better, but those cost over $600.
The resolution is how many dots there are on a screen, like megapixels in a digital camera. The more dots, the crisper the image.
Your scoreboard is displaying gigantic numbers to people maybe 100 feet away. You don't have to care about resolution.
The Derby Dames bought an 800x600 projector, which is more than enough for a scoreboard, and can even do 720p (for DVDs).
A good projection screen can really help make your scoreboard more visible. They are also terribly expensive for the size you will need at a bout.
Find some way to hang a queen-size white bed sheet vertically and call it good enough. If you have any team members or fans who like nailing boards together, you can whip up a decent structure out of scrap lumber. Remember, it doesn't need to look pretty: you're going to cover it up with a sheet.
You can run all of this for about $650 new, maybe under $400 if you shop around for used equipment.
Ask me questions! I like to help!Neale Pickett