There is a parameter in module configuration called "Delay for auto play". Just enter a number (in seconds) and that will control the speed.

If you mean the speed of actual transition that's something else.

Currently not as it's different for different effects. Which effect do you use?
Maybe I will add it to parameters in a later version.

Vertical scroll all right, but which effect (Linear, Expo, Bounce or Back)? Each transition has different transition time.

I visited your site and I see that you use linear transition. Open the file modules/mod_ajaxscroller/mod_ajaxscroller/script.js

Find the code: "linear|500|". Change this to "linear|1000|" or any other value in milliseconds you would like the transition to take.