Gateway roles have no specific hardware configuration requirements. A gateway role simply copies the configuration files needed for a given role to be accessed from a host outside of the cluster. The hardware configuration will depend on what your team will be doing on the host.
Here is a link to the documentation on managing roles:
Agatewayis a special type of role whose sole purpose is to designate a host that should receive a client configuration for a specific service, when the host does not have any roles running on it. Gateway roles enable Cloudera Manager to install and manage client configurations on that host. There is no process associated with a gateway role, and its status will always be Stopped. You can configure gateway roles for HBase, HDFS, Hive, Kafka, MapReduce, Solr, Spark, Sqoop 1 Client, and YARN.