Not sure on just one call but cant you have a pdoResouces with no sort calling a chunk with another pdoResouces in it for just the RAND and the chunk to use for display, might work ?
I'm assuming you want to do this in order to randomise a subset of the data in your table. A database-centric way of doing this is to create a view that contains the subset data and then use the same pdoResources call but on the view rather than the table.
I'm a big fan of having the database do as much work as possible...
