System Generator: How to make an implementation a mathematical function through a ROM
Use a ROM block (from the memory section of the Xilinx blockset).

It has a parameter called Inital value vector - put the name of the vector in there.  Put length(vector_name) in the depth parameter.  

Setup the output type tab to the fixed point representation you want to use.  Bear in mind the sizes of RAM bclock you have available in the target FPGA when selecting the number of bits. For example, 2k elements of 9 bits fits just as well in a single RAM block as 2k elements of 8 bits (in case you, or other readers, aren't already aware of that).

Job done!