How to configure role to edit only specific nodes by field?
This looks like an ideal case for one of the Taxonomy access modules.

There are several to choose from, though I favour 
Taxonomy Access Control Lite as it also allows you to grant access to individuals (should the need arise) as well as giving access rights based on roles.

The basic setup would be:-


Create a Taxonomy of the different kinds of event that you wish to use.
Give each "Event" node a Taxonomy reference field, that references the values from the Taxonomy that you setup in step 1.
Install and activate Taxonomy Access Control Lite via your preferred method.
Configure the access for each role to the Taxonomy from step 1. via the TAC lite configuration screen.  There are options to control the viewing, updating, and deletion of nodes, as well as the visibility of the Taxonomy terms in selection lists - which prevents users creating nodes tagged with event types that they don't have access to.


I hope that helps.