The short answer: it depends.
The long answer: if an item doesn't have an effect and cannot be rolled anywhere on the site, you can still have one. However, the complexity and specific item you want may require you to do some work for it. For instance, while a character is generally allowed to start off with one or two useless little trinkets, if you want them to get more, you have to explain it. If you want a relatively unimpressive item such as a gold coin, a ribbon with no use or some generic survival supplies such as food and medical supplies (that aren't already available on the site), you can have your character find them in a thread or even just already be carrying them at the start of the thread. For particularly complex items, people generally either buy them or collect things that they could use to explain making the item in question. I suppose an outlaw could just steal whatever they want. In some cases, extremely complex (or ridiculous) items just won't be allowed.
There are no concrete rules regarding this topic, so if you want something, ask the admins about it.