Could you give me more details what do you wish to achieve? Roles by definition are the groups of users with the same permissions set. So 200 users with unique roles, finally 200 roles is little beyond the usual permissions model. WordPress is not designed for the very large quant of roles:
– all roles are loaded to the memory at once;
– Roles a listed as the views at the top of users list. Imagine how the “Users” page will be looked with 200 views links at the top. With 1 user at every view such views will have no sense
– Role selection user interface is realized as a drop-down list at the most of places including User Role Editor itself. So such controls will become unusable with 200 roles inside.
May be you need to re-design your idea and use some other WordPress feature, e.g. user metadata, etc. to differentiate users from each other?
One of potential variants: it’s possible to assign some unique capability to every user directly, not via role. It depends where do you plan to use this flag/value. Will it be really used as the part of permissions system or for some other purpose, like reporting, classification, etc.?