All prices (short as well as long term stays) can be determined by yourself. myroom24 does not give you any specifications regarding the pricing. However, please note that the price is one of the most important decision criteria for guests looking for accommodation. No matter how nice your accommodation may be: If it is more expensive than comparable offers in the area, you may well miss out on bookings.
Please also remember that the price you set is not the final price guests will pay. To set a price that works for you and your guests, you should consider the guest service fee, any additional fees you want to charge (such as fees for cleaning and additional guests), and taxes, in your area.