Some species can be housed together in a large enough space. 

Cohabitation

Mantids:
Keeping mantids together regardless of species comes with a chance of cannibalisms.  Mantids are opportunistic hunters meaning they will take any advantage over their fellow mantids if it means an easy meal. Females are more likely to do this, especially if their target is a male. Males in general are smaller than females at the same instar. A weaker or smaller mantis is an opportunity of a quick snack

Some species can be quite docile to each other and can be kept in small groups with enough space and food. As ambush predators, their main strategy is to stay in one place and wait for prey to come within range of them. With a large enough enclosure some species will stay in one location and have little interact with each other. 

If you do decide to keep more than one mantis, be sure to research which can be housed together. Keeping males and females separated can also reduce any cannibalisms.


Other Invertebrates:
Mantids will eat anything they can successfully catch, meaning most other invertebrates you may decide to keep are a free meal to a mantis.

Some things can be kept in the same enclosure and can even be beneficial such as isopods and springtails. These can be used as a cleanup crew to removing organic waste from enclosures. They spend their time on the ground and under leaf litter so they rarely interact with a mantis. Small mantids like boxer species will hunt springtails for food during their first and second instar however. 

Vertebrates:
Keeping any kind of vertebrate together with a mantis is not recommended. Small snakes, lizards, mice and birds can end up a meal for a hungry large mantis. The mantis could be a meal for anything bigger than its self as well. Any of these can bite or cause harm to the mantis causing injury or death.  A large snake could accidently crush an unseen mantis.