The Pumas launched a late onslaught in Cardiff but were unable to grab a win which would have boosted morale ahead of the World Cup.
However, Roncero was not particularly despondent despite the setback.
He said: “In the first half, we made childish mistakes.
“To win was not the main thing but we were looking forward to giving a greater identity to the team.”
Felipe Contepomi, who played at centre despite an outstanding display against Ireland earlier this year at fly-half, was also unconcerned.
“We need more time playing together,” he said. “We shouldn’t be too desperate over this.”
Federico Serra believed a more measured approach could pay dividends.
He said: “I think we need more patience in some situations. In the second half we changed our plan and that’s a good thing.
“There are several things to correct. We made quite a lot of mistakes indefence during the first half,” said Serra.
“In these kind of Tests we cannot give away those types of errors.”
Argentina’s final warm-up game before the World Cup in France comes next Saturday when they meet a Belgium XV in Brussels.
One player who will hope to take part is centre Martin Gaitan, who suffered a “cardiac problem” after the Wales game.
He fainted in the dressing room and was rushed to hospital where it wasdiscovered one of his arteries was dilated.
Tries: G. Thomas, Wyn-Jones, M. Jones. Cons: Hook 3. Pens: Hook 2.
Tries: Corleto 2. Cons: Todeschini 2. Pens: Todeschini 2.
Morgan, D. James, Shanklin, G. Thomas, M. Jones, Hook, Peel, Popham, Williams, J. Thomas, Wyn-Jones, Gough, A. Jones, Rees, D. Jones.
Replacements: Robinson for G. Thomas (66), Charvis for Williams (68), W. James for Gough (61), Jenkins for D. Jones (58).
Miras, Borges, Gaitan, F. Contepomi, Corleto, Todeschini, Pichot, Longo Elia, J. Fernandez Lobbe, Leguizamon, Albacete, C. Fernandez Lobbe, Scelzo, Ledesma, Roncero.
Durand for Leguizamon (61), Kairelis for C. Fernandez Lobbe (61), Bonorino for Scelzo (61).
C White (RFU).