If you do not have a specified term for the lease, your oral lease can be terminated by the landlord. Who is you landlord? If the roommate is the one that brought you in, then quite possibly, either the roommate or roommate's landlord can give you notice and evict you. A month-to-month tenancy only requires fifteen days notice prior to the end of the monthly period.
Fla. Stat. 83.46 Rent; duration of tenancies.--
(1) Unless otherwise agreed, rent is payable without demand or notice; periodic rent is payable at the beginning of each rent payment period; and rent is uniformly apportionable from day to day.
(2) If the rental agreement contains no provision as to duration of the tenancy, the duration is determined by the periods for which the rent is payable. If the rent is payable weekly, then the tenancy is from week to week; if payable monthly, tenancy is from month to month; if payable quarterly, tenancy is from quarter to quarter; if payable yearly, tenancy is from year to year.
(3) If the dwelling unit is furnished without rent as an incident of employment and there is no agreement as to the duration of the tenancy, the duration is determined by the periods for which wages are payable. If wages are payable weekly or more frequently, then the tenancy is from week to week; and if wages are payable monthly or no wages are payable, then the tenancy is from month to month. In the event that the employee ceases employment, the employer shall be entitled to rent for the period from the day after the employee ceases employment until the day that the dwelling unit is vacated at a rate equivalent to the rate charged for similarly situated residences in the area. This subsection shall not apply to an employee or a resident manager of an apartment house or an apartment complex when there is a written agreement to the contrary.
Fla. Stat. 83.57 Termination of tenancy without specific term.--A tenancy without a specific duration, as defined in s. 83.46(2) or (3), may be terminated by either party giving written notice in the manner provided in s. 83.56(4), as follows:
(1) When the tenancy is from year to year, by giving not less than 60 days' notice prior to the end of any annual period;
(2) When the tenancy is from quarter to quarter, by giving not less than 30 days' notice prior to the end of any quarterly period;
(3) When the tenancy is from month to month, by giving not less than 15 days' notice prior to the end of any monthly period; and
(4) When the tenancy is from week to week, by giving not less than 7 days' notice prior to the end of any weekly period.