For Easy Agile Roadmaps Versions 3.2 through to 3.3.7, it is possible to search for scheduled issues on the roadmap using JQL / Advanced Search.

Examples 

Search

JQL query

Find all scheduled issues

issue.property[EA-schedules].tags is not empty

Find all issues scheduled in Q3 2018

issue.property[EA-schedules].tags ~ "2018_3"

As of Easy Agile Roadmaps 4.0, issues scheduled on the Roadmap can be synced with the Jira Start and Due Date fields. 

Issues scheduled on the Roadmap are then searchable via JQL using their respective Start and Due Date names.