The max number of spaces is configurable and defaults to 1000.
Spaces should have no impact on cluster performance since they are not an Elasticsearch construct (Kibana only).
Looks like there's no limit other than disk space to the number of roles (source).
As far as roles impacting performance: my colleague says that hundreds is fine, millions is likely to have some impact. Numbers in the middle might have limited impact—you'd just have to feel your way.
Let me know if this helps!