Strawberries are worse than Romaine to check for infestation. Romaine lettuce can be checked if one is expert and has the required equipment. Strawberries are infested with thrips that hide under the seeds & it's impossible to see them till they come out.
Therefore fresh strawberries must be peeled completely.
All of the frozen strawberries with a hashgocha or Ishur must be cooked, pureed, etc prior to use.