Switch couples:
http://www.mangago.zone/read-manga/playtime_with_hakdo/?sYU5
http://www.mangago.zone/read-manga/dark_heaven/?zlJz
This one too but idk if I'd recommend it: http://www.mangago.zone/read-manga/nigai_no_theme/
This one: http://www.mangago.zone/read-manga/sojou_no_koi_wa_nido_haneru/ they're like that but it's a sequel, I'd recommend you read first the first volume. I'll leave the link here http://www.mangago.zone/read-manga/kyuuso_ha_cheese_no_yume_omiru/ (they switch in the first volume too but it's not a smooth kind of switch at all)
http://www.mangago.zone/read-manga/to_dear_my_sorrow/ here they switch but I think it's a one time thing
http://www.mangago.zone/read-manga/like_a_tidal_wave_from_pheromone_shower/ they switch at a certain point but stick to those roles from then on
http://www.mangago.zone/read-manga/neko_x_neko/ same as above
http://www.mangago.zone/read-manga/wagging_the_tail/ the bottom tops in one of the last chapters if not really the last one
These ones they never switch while in the relationship but maybe change from top to bottom or vice versa
http://www.mangago.zone/read-manga/kuro_ouji_no_iinari_ni_naranai/ I don't think it's shown but here they both had fixed roles with other people but switched them with each other
http://www.mangago.zone/read-manga/life_ain_t_so_bad/ one of them usually bottoms but tops for the other (I think they also try to switch but I'm not sure)
http://www.mangago.zone/read-manga/puchitto_hajiketa/ one of them only tops but bottoms for the other
http://www.mangago.zone/read-manga/eunsuk_jung_gu/?ro1Q one of them bottoms (for work) and only tops for the other
That's all I have (づ ̄ ³ ̄)づ
gimme bunch of switches yaoi onegai