Hello Asim Haque,

Being adherent in nature, HEK293 TT cells will not prefer the roller bottle because the roller bottle provides a rotating surface for cell attachment and these cells prefer a more stable, flat surface for optimal growth. Moreover, the constant rolling motion can disrupt cell attachment and lead to cell detachment, especially if the cells are not well-attached or if the culture is not optimized for roller bottle conditions. 

You may first adapt HEK293 TT cells to suspension culture for your type of application. The standard HEK293 TT cells from ATCC are not inherently suspension-adapted. 

Adapting adherent culture to suspension culture may be done as follows.

Maintain your adherent cells in a standard culture medium with a standard serum concentration (like 10% FBS). Then gradually decrease the serum concentration over several passages, for instance, 10%, 5%, 2%, 1%, 0.5%, and finally 0% (serum-free).

At each step, observe cell growth and viability. If cells appear unhealthy (e.g., low viability, slow growth), increase the serum concentration back to the previous level until the cells recover. Keep the cell density within the recommended range for HEK293 TT cells throughout the adaptation process. 

Once your cells are adapted to low serum or serum-free conditions and growing well, detach them from the adherent surface using standard procedures (like trypsinization). Resuspend the cells in the desired suspension culture medium (the same medium you used for adherent culture, but with a low serum concentration or serum-free). Seed the cells into roller bottles at a suitable density (say 0.5-1 x 10^6 cells/ml). Please note that you will have to observe the culture daily for cell growth and viability. You may need to adjust the seeding density or medium composition during the adaptation process. Once the cells are adapted to suspension and serum-free conditions, you can scale up the culture using appropriate bioreactors for your experiments. 

Sometimes, cells may clump during the adaptation phase. In such a case, adding a surfactant like Poloxamer 188 can help prevent cell clumping and improve viability in suspension culture.

Good Luck!