If you feel its difficult to work in two roles then inform your management that it is not possible to work in both roles.
According to me this situation should handled by mutual understanding, If you will make this situation more critical then it effects your employment.
You may ask your management for compensation for dual role responsibility, If they not agree with this, then search for new job which comfortable for you, If you want to fight legally, Ask yourself, do you have that much of time to do all.
The law, however, is not applicable to all institutions, as not every organisation falls within the meaning of factory under the Factories Act, 1948. Organisations that are not covered by the Factories Act must specify the stipulation related to double employment by way of dual employment clause in appointment letter or employee’s agreement or offer letter. The employment agreement must state what restrictions have been placed on double employment and that the employee is prohibited from engaging in an additional employment or profession till they’re under their current employer’s services. That means that an employee can not take up dual jobs.
When there is no legal obligations of Dual employment then their is no legal obligations on dual role also.