From the studio's homepage Bulletin Board in 2009

制作遠藤達也 said:
赤也の特訓とリョーマ・金太郎のラリーは社内の作画さんが

Credited in-house artists: Miyuki Ueda (上田美由紀), Aya Nakanishi (中西彩), and Naoko Ise (伊勢奈央子)
Yousuke Okuda (奥田陽介) is also on the episode but I'm not sure if they were in-house at M.S.C at this time, or ever.
It's also worth noting that Jun Watanabe was AD on this episode and may have been omitted from the KA list.