Final answer:
The grammatically incorrect sentence is 'Roberto está jugando al fútbol los martes.' The correct sentence is 'Roberto juega al fútbol los martes.'
Step-by-step explanation:
The grammatically incorrect sentence is Roberto está jugando al fútbol los martes. In Spanish, when expressing a habitual action, we use the simple present tense rather than the present continuous tense. Therefore, the correct sentence would be Roberto juega al fútbol los martes. This sentence means 'Roberto plays soccer on Tuesdays'.
Learn more about Spanish sentence structure