Search/transactions not support in oasisprotocol/oasis-rosetta-gateway

networkAPIController := server.NewNetworkAPIController(
	services.NewNetworkAPIService(oasisClient), asserter,
)
accountAPIController := server.NewAccountAPIController(
	services.NewAccountAPIService(oasisClient), asserter,
)
blockAPIController := server.NewBlockAPIController(
	services.NewBlockAPIService(oasisClient), asserter,
)
constructionAPIController := server.NewConstructionAPIController(
	services.NewConstructionAPIService(oasisClient), asserter,
)
mempoolAPIController := server.NewMempoolAPIController(
	services.NewMempoolAPIService(oasisClient), asserter,
)

that’s true, you’ll have to use other software to search. GitHub - oasisprotocol/oasis-indexer: The official indexer for the Oasis Network.