Looking at the main documentation page for Signal Processing Toolbox it does not appear this product contains any Simulink blocks. Nor does the main documentation page for RF Toolbox list a Blocks header. The blocks associated with designing RF systems are part of RF Blockset as you can see from the Blocks entry in the header immediately above the name RF Blockset on that page.
If you know the functionality you were expecting to be available as a block in Signal Processing Toolbox you could search the alphabetical list of blocks to determine which product contains a block for that functionality (or determine if such a block exists.)
