The optimal time to slow roll swimbaits for big bass can vary depending on the conditions and the behavior of the fish. However, there are a few key factors to consider.

First, slow rolling swimbaits is often most effective during the pre-spawn and post-spawn periods. These are times when bass are actively feeding and can be more aggressive towards larger prey. The pre-spawn period typically occurs in the early spring when bass are moving towards their spawning areas, while the post-spawn period happens after the bass have finished spawning and are recovering.

Second, the water temperature can also play a role in determining when to slow roll swimbaits. Bass tend to be more active and willing to chase down a bait when the water is warmer. As the water temperature rises, usually in the late spring and summer, bass become more active and may be more responsive to a slow rolled swimbait.

Lastly, the depth at which you are fishing can also impact the effectiveness of slow rolling swimbaits. In the videos provided, it is mentioned that slow rolling swimbaits can be effective in deeper water, such as 20 feet or more. This is because the slow rolling retrieve allows the swimbait to stay in the strike zone for a longer period of time, increasing the chances of enticing a big bass to bite.

It's important to note that these are general guidelines and there can be exceptions depending on the specific fishing location and conditions. It's always a good idea to observe the behavior of the fish and adjust your techniques accordingly. Additionally, if you have any specific questions about slow rolling swimbaits or need further clarification, please let me know.