It depends. If the plan in which the retirees are enrolled also covers active workers, relevant consumer protections will apply, including limits on out-of-pocket costs and coverage of recommended preventive services without cost-sharing. However, if the plan only covers retirees, as is more often the case, the coverage does not have to comply with the Affordable Care Act consumer protections. Your former employer can tell you which type of plan you have.
On Private Health Insurance Coverage & The Health Insurance Marketplace