I play with a double bass, and it took me about an hour to get a roll going. It was easy for me because I am left handed, but I play drums like a right handed person.
Ok, I believe that, but for us mere mortals I would not put I time limit on your double bass playing (a click yes, a clock no!) and just work on it every day for as long as you can. Stretch your feet and ankles a bit before playing to slow down the "burn". Try to get thru all the subdivisions between clicks/quarter notes however you want to define it and play 2's 3's 4's 5's 6's 7's and 8's singles. If you want to do doubles and diddles and flams with your feet ok, but I suggest you get your hands really smoking first and make sure all your fundamentals are happening.
It never stops....one can always play faster or with more power- just keep working at it...or you can cheat and play quads. Make sure you get your quads happening...they are simple to play, but trickier to fit in a bar of music correctly. *yawn* play eighth note triplets then squeeze in a RL with your hands and a RL on your double kick in the same time as you would normally play the sequence of 8th note trips. Ya all are artificial grouping now...ain't it fun?
WOW...now you are rolling!