The executive head of state in India is the President. This position is the highest constitutional office in India and is responsible for representing the country both nationally and internationally.

Roles and Responsibilities of the President:
1. Head of the State: The President is the Head of the State and represents India internationally.
2. Executive Power: The President is the executive head of the government and all executive actions are taken in his/her name.
3. Commander-in-chief: The President is the supreme commander of the Indian Armed Forces.
4. Legislative Power: The President has the power to summon and prorogue both the Houses of the Parliament and can dissolve the Lok Sabha.
5. Judicial Power: The President can grant pardons, reprieves or remissions of punishment to convicts.
6. Appointments: The President appoints the Prime Minister, judges of the Supreme Court and High Courts, Governor of States, etc.

Selection of the President:
1. The President is elected by an Electoral College comprising of Members of Parliament and Members of Legislative Assemblies of States.
2. The election is held through a secret ballot.
3. The candidate who secures more than 50% of the votes is declared the winner.

Tenure of the President:
1. The President's term is five years.
2. The President can be re-elected for a second term.
3. The President can resign before completing the term.

In conclusion, the President is the executive head of state in India and holds significant powers and responsibilities. The position is elected through an Electoral College and has a five-year tenure, which can be renewed for another term.