Equating a value to single root within all values of RootOf

I have a variable that can take multiple values since it is the RootOf solution of a polynomial. Based on the setup of the problem, the variable should be between 0 and 1, and therefore should be only one of the four values spitted out by the allvalues of the RootOf function. How can I make Maple understand that this variable should only take one of the four values that is the outcome of allvalues of the RootOf function? Can I define this variable to be between 0 and 1 upfront? If not, how do you make Maple "pick" only one value out of multiple outcomes of allvalues evaluation?