repro.sh

#!/bin/bash
TMP_DIR=tmp_include_roles_repro

mkdir -p $TMP_DIR/roles/{x,y}/tasks
cat > $TMP_DIR/playbook.yml << EOF
- hosts: localhost
  tasks:
    - set_fact:
        role_name_in_fact: "x"

    - name: role name stored in a fact
      include_role:
        name: "{{ role_name_in_fact }}"
EOF
ansible-playbook $TMP_DIR/playbook.yml -vvv
rm -rf $TMP_DIR/