The midfielder had a brief spell with the Pics in 2020/21 before moving on to Hemel Hempstead Town of National League South.
Mantom, who began his professional career at Albion, amassed more than 150 appearances in the Walsall before going on to play for Scunthopre United and Southend United.
“I am absolutely delighted to get Sam on board,” said manager Liam McDonald. “Having already had a spell here, he knows the club and what we are all about.
“He really wanted to come here, which is so important. He’s an outstanding footballer and this is just a massive coup for the club.
“He captained Walsall and was skipper at the level above last season, so we know how good he is going to be in the dressing room.
“I am over the moon that he has chosen us over a lot of other options and he will be key to our success in the season ahead.
“He’s a local lad and this is an ideal situation for all concerned and I know that our fans will be pleased with this signing.”
The Pics have also announced the captures of midfielder, Jack Burgess, from Sutton Coldfield Town, and powerful frontman Alex Cameron.
Rushall are a reduced-rate pre-season bundle for their home friendlies via rushallolympicfc.ktckts.com – the ‘Pics Power Bundle’ is £35 per adult, £25 concessions and £12.50 for under-16s.