Those are grow rocks. Doing a full grow like you have pictured may be a problem. You can put some garden netting down on the bottom for the roots to grab a hold of and one on the top for the plants to grow through but not much else is practical.

When the plants get older and taller they will top over, plants that don't have a good strong root will not grow as fast as those that have a good footing to hold the plant.

You can tie each plant to the roof to hold it in place that would work as well but a shit load of work.

Are you going to grow full term with that system?